CriticalCVE-2016-5195

    Linux Kernel Race Condition Vulnerability (CVE-2016-5195)

    Published In CISA KEV since Sources: CVE.org

    What is affected, what to do

    Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect handling of a copy-on-write (COW) feature to write to a read-only memory mapping, as exploited in the wild in October 2016, aka "Dirty COW."

    The vulnerability is being actively exploited; treat it as a priority. Update Linux Kernel to version 3.2.83, Linux Kernel to version 3.4.113, Linux Kernel to version 3.10.104. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Canonical Ubuntu Linux eq 12.04..12.04
    • Canonical Ubuntu Linux eq 14.04..14.04
    • Canonical Ubuntu Linux eq 16.04..16.04
    • Canonical Ubuntu Linux eq 16.10..16.10
    • Linux Kernel lt 2.6.22..3.2.83
    • Linux Kernel lt 3.3..3.4.113
    • Linux Kernel lt 3.5..3.10.104
    • Linux Kernel lt 3.11..3.12.66
    • Linux Kernel lt 3.13..3.16.38
    • Linux Kernel lt 3.17..3.18.44
    • Linux Kernel lt 3.19..4.1.35
    • Linux Kernel lt 4.2..4.4.26
    • Linux Kernel lt 4.5..4.7.9
    • Linux Kernel lt 4.8..4.8.3
    • Redhat Enterprise Linux eq 5..5
    • Redhat Enterprise Linux eq 6.0..6.0
    • Redhat Enterprise Linux eq 7.0..7.0
    • Redhat Enterprise Linux Advanced mission critical Update Support (AUS) eq 6.2..6.2
    • Redhat Enterprise Linux Advanced mission critical Update Support (AUS) eq 6.4..6.4
    • Redhat Enterprise Linux Advanced mission critical Update Support (AUS) eq 6.5..6.5
    • Red Hat Enterprise Linux Extended Update Support (EUS) eq 6.6..6.6
    • Red Hat Enterprise Linux Extended Update Support (EUS) eq 6.7..6.7
    • Red Hat Enterprise Linux Extended Update Support (EUS) eq 7.1..7.1
    • Red Hat Enterprise Linux Long Life eq 5.6..5.6
    • Red Hat Enterprise Linux Long Life eq 5.9..5.9
    • Red Hat Enterprise Linux (TUS) eq 6.5..6.5
    • Debian Linux eq 7.0..7.0
    • Debian Linux eq 8.0..8.0
    • Fedora eq 23..23
    • Fedora eq 24..24
    • Fedora eq 25..25
    • Palo Alto Networks PAN-OS lt 5.1..7.0.14
    • Palo Alto Networks PAN-OS lt 7.1.0..7.1.8
    Fixed in
    • Linux Kernel 3.2.83
    • Linux Kernel 3.4.113
    • Linux Kernel 3.10.104
    • Linux Kernel 3.12.66
    • Linux Kernel 3.16.38
    • Linux Kernel 3.18.44
    • Linux Kernel 4.1.35
    • Linux Kernel 4.4.26
    • Linux Kernel 4.7.9
    • Linux Kernel 4.8.3
    • Palo Alto Networks PAN-OS 7.0.14
    • Palo Alto Networks PAN-OS 7.1.8

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    7.0

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    7.0

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org

    83.5 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.68

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    214.49 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    7.0 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.0
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    83.5 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.68
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary

    Response and mitigation

    Why act now?

    Prioritisation rationale

    Dirty COW is a local privilege escalation: the attacker needs existing code execution as an ordinary user. However, reliable public exploits have been around for years, it ranks among the CVEs most likely to be exploited, and its nominally high attack complexity barely matters in practice. Attackers typically use it as a second stage after a web shell, a stolen SSH account or a malicious app (Android) to gain root, establish persistence and harvest credentials. CISA does not flag ransomware use. Today the real residual exposure sits in legacy servers, appliances, OT and embedded devices. Rate these high for KRITIS operators if they are reachable from user or application zones, and medium if they are strictly isolated and host no third-party local accounts.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Collect kernel versions across all Linux hosts (uname -r, via Ansible/Salt/EDR inventory). Mainline kernels before 4.8.3 are vulnerable. Distribution kernels (Ubuntu 12.04/14.04/16.04/16.10, Debian 7/8, Fedora 23/24) ship backported fixes under their own version numbers. Look up the fixed package version in the relevant distro advisory (USN, DSA, Fedora update).
      • Patch the kernel and reboot: Install the patched distro kernel and reboot. Without a reboot, the vulnerable kernel stays live. Where no reboot window exists, use live patching (Canonical Livepatch, kpatch, kGraft) and confirm the patch is actually loaded.
      • Flag assets with no patch path: Track EOL distributions, appliances, embedded/IoT devices and Android-based endpoints separately. Many of these will never get a vendor fix. Check the vendor advisory, then plan isolation or replacement.
      • Multi-user and container hosts first: Prioritise systems with untrusted local users: shared hosting, jump hosts, CI runners, container hosts, and web servers that allow uploads or code execution. On these hosts, any foothold becomes root immediately.
      • Compromise check: Verify /etc/passwd, /etc/shadow and SUID binaries (e.g. /usr/bin/passwd) against package hashes (debsums -c, rpm -Va). Hunt for extra UID 0 accounts. If you find anything, treat the host as fully compromised and rotate every credential stored on or used from it.

    2. Runbook step 2

      Mitigation layers

      • Access control / IAM: Minimise local shell access. Disable unused accounts and restrict SSH to MFA-protected bastions. On a vulnerable kernel, any local code execution equals root.
      • Application layer: Harden web and app servers running vulnerable kernels, because the standard chain is web shell or RCE → Dirty COW → root. Use WAF rules for upload abuse and web shell patterns, and noexec mounts on /tmp, /var/tmp, /dev/shm and upload directories.
      • Endpoint hardening: Set kernel.yama.ptrace_scope=2 or 3. This stops the ptrace variant (PTRACE_POKEDATA) but not the /proc/self/mem variant, so treat it as a partial control only.
      • Container isolation: Enforce seccomp profiles that deny ptrace (Docker default profile, no --privileged containers). Containers share the host kernel, and the public vDSO variant enables container escape. Do not treat an unpatched container host as a security boundary.
      • Network segmentation: Move unpatchable legacy systems and appliances into dedicated VLANs. Allow inbound management only via jump hosts, and block outbound internet so attackers cannot pull exploit binaries.
      • Vendor-specific: RHEL-family vendors published temporary workarounds. Look up the details in the vendor advisory. They do not replace a kernel update.

    3. Runbook step 3

      Detection rules

      • auditd – ptrace variant: -a always,exit -F arch=b64 -S ptrace -F a0=0x5 -k dirtycow_ptrace (PTRACE_POKEDATA). Alert when the caller is not a known debugger (gdb, strace) and runs as an unprivileged user.
      • auditd/FIM – file tampering: -w /etc/passwd -p wa -k passwd_mod and -w /usr/bin/passwd -p wa -k suid_mod, plus AIDE/Wazuh FIM on SUID binaries. Common public exploits leave artefacts such as /tmp/passwd.bak and create a UID 0 account (default name firefart). Hunt with awk -F: '$3==0' /etc/passwd.
      • Sysmon for Linux / EDR – process ancestry: Look for a process descended from a web or service user (www-data, apache, nginx, tomcat) that spawns a shell with euid=0 shortly after running an unknown binary from /tmp or /dev/shm. Example KQL: DeviceProcessEvents | where InitiatingProcessAccountName in ("www-data","apache") and AccountName == "root" and FileName in ("bash","sh").
      • Build artefacts: Watch for service accounts invoking gcc/cc with -pthread, and for files named dirty, dirtyc0w, cowroot or pokemon in /tmp. Sigma shape: process_creation | Image endswith '/gcc' AND User in (service_accounts).
      • Auth logs: Check /var/log/auth.log or secure for successful su/login events by unfamiliar UID 0 accounts, and for root sessions with no preceding sudo entries.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect handling of a copy-on-write (COW) feature to write to a read-only memory mapping, as exploited in the wild in October 2016, aka "Dirty COW."

    Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    netappcloud_backup
    • —
    • —
    netapphci_storage_nodes
    • —
    • —
    netapponcommand_balance
    • —
    • —
    netapponcommand_performance_manager
    • —
    • —
    netapponcommand_unified_manager_for_clustered_data_ontap
    • —
    • —
    netappontap_select_deploy_administration_utility
    • —
    • —
    netappsnapprotect
    • —
    • —
    netappsolidfire
    • —
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebiandebian_linux7.0
    Linuxdebiandebian_linux8.0
    Linuxredhatenterprise_linux5
    Linuxredhatenterprise_linux6.0
    Linuxredhatenterprise_linux7.0
    Linuxredhatenterprise_linux_aus6.2
    Linuxredhatenterprise_linux_aus6.4
    Linuxredhatenterprise_linux_aus6.5
    Linuxredhatenterprise_linux_eus6.6
    Linuxredhatenterprise_linux_eus6.7
    Linuxredhatenterprise_linux_eus7.1
    Linuxredhatenterprise_linux_long_life5.6
    Linuxredhatenterprise_linux_long_life5.9
    Linuxredhatenterprise_linux_tus6.5
    Linuxlinuxlinux_kernel—
    Linuxcanonicalubuntu_linux12.04
    Linuxcanonicalubuntu_linux14.04
    Linuxcanonicalubuntu_linux16.04
    Linuxcanonicalubuntu_linux16.10
    Otherfedoraprojectfedora23
    Otherfedoraprojectfedora24
    Otherfedoraprojectfedora25
    Otherpaloaltonetworkspan-os—

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    Reference tagged as exploitbugzilla.redhat.com (opens in a new tab)PoC (publicly reported)reported, not verified—
    Reference tagged as exploitgithub.com (opens in a new tab)PoC (publicly reported)reported, not verified—
    Packet StormKernel Live Patch Security Notice LSN 0012 1 (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormDirtyCow Linux Kernel Race Condition (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormDirtyCow Local Root Proof Of Concept (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormLinux Kernel Dirty COW PTRACE_POKEDATA Privilege Escalation (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormLinux Kernel Dirty COW PTRACE_POKEDATA Privilege Escalation (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormKernel Live Patch Security Notice LSN 0021 1 (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Exploit-DBEDB-ID 40611 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—
    Exploit-DBEDB-ID 40616 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—
    Exploit-DBEDB-ID 40839 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—
    Exploit-DBEDB-ID 40847 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—
    PoC-in-GitHub (nomi-sec)CVE-2016-5195 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)CVE-2016-5195 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)lenovo-a1000g-mt8317-A412_01_09_130907-kernel-3.4.0-root-cve-2016-5195 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)Exploit-Dirty-Cow (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)kernel-exploit-dirtycow (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • rhn.redhat.comRHSA-2016:2107Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • exploit-db.com40616Exploit, x_refsource_EXPLOIT-DB, Exploit, Third-party advisory, Vulnerability database
    • access.redhat.comRHSA-2017:0372Vendor advisory, x_refsource_REDHAT, Broken link, Third-party advisory
    • bto.bluecoat.comsecurity-advisory/sa134x_refsource_CONFIRM, Permissions required, Third-party advisory
    • h20566.www2.hpe.comportal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05352241x_refsource_CONFIRM, Third-party advisory
    • oracle.comtechnetwork/security-advisory/cpujul2018-4258247.htmlx_refsource_CONFIRM, Patch, Third-party advisory
    • exploit-db.com40839Exploit, x_refsource_EXPLOIT-DB, Exploit, Third-party advisory, Vulnerability database
    • dirtycow.ninjax_refsource_MISC, Third-party advisory
    • exploit-db.com40847Exploit, x_refsource_EXPLOIT-DB, Third-party advisory, Vulnerability database
    • rhn.redhat.comRHSA-2016:2118Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • rhn.redhat.comRHSA-2016:2128Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • source.android.comsecurity/bulletin/2016-12-01.htmlx_refsource_CONFIRM, Third-party advisory
    • rhn.redhat.comRHSA-2016:2120Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • openwall.com[oss-security] 20161026 Re: CVE-2016-5195 "Dirty COW" Linux kernel privilege escalation vulnerabilityMailing list, x_refsource_MLIST, Mailing list, Third-party advisory
    • rhn.redhat.comRHSA-2016:2133Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • rhn.redhat.comRHSA-2016:2098Vendor advisory, x_refsource_REDHAT, Third-party advisory
    • h20566.www2.hpe.comhpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbgn037…x_refsource_CONFIRM, Third-party advisory
    • kb.cert.orgVU#243144Third-party advisory, x_refsource_CERT-VN, Third-party advisory, US government resource
    • bugzilla.suse.comshow_bug.cgi?id=1004418x_refsource_CONFIRM, Issue tracking
    • securitytracker.com1037078Vulnerability database, x_refsource_SECTRACK, Broken link, Third-party advisory, Vulnerability database

    Linked advisories

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