CriticalCVE-2026-98432

    Linux Kernel: Use-After-Free (CVE-2026-98432)

    Published Last modified Sources: Debian LTS, Debian, SUSE, BSI, pwn.watch, CVE.org, Msrc Update Guide

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: ipv4: free inet_opt and ireq_opt after an RCU grace period tcp_v4_syn_recv_sock() transfers ownership of ireq->ireq_opt to the child socket (newinet->inet_opt) without copying it. Another cpu can concurrently process a retransmitted SYN for the same request socket, and send a SYNACK from tcp_check_req(). tcp_v4_send_synack() and inet_csk_route_req() read ireq->ireq_opt under rcu_read_lock() only, and ip_build_and_send_pkt() and ip_options_build() then read opt->optlen twice.

    Update Linux Kernel to version 5.10.272, Linux Kernel to version 5.15.223, Linux Kernel to version 6.1.190.

    Affected
    • Linux Kernel lt 4.4..5.10.272
    • Linux Kernel lt 5.11..5.15.223
    • Linux Kernel lt 5.16..6.1.190
    • Linux Kernel lt 6.2..6.6.159
    • Linux Kernel lt 6.7..6.12.113
    • Linux Kernel lt 6.13..6.18.56
    • Linux Kernel lt 6.19..7.2.10
    Fixed in
    • Linux Kernel 5.10.272
    • Linux Kernel 5.15.223
    • Linux Kernel 6.1.190
    • Linux Kernel 6.6.159
    • Linux Kernel 6.12.113
    • Linux Kernel 6.18.56
    • Linux Kernel 7.2.10
    • Linux Kernel 7.3

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

    Metrics

    9.8

    Priority

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

    Source: Vendor (CNA), CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: Debian LTS, Debian, SUSE, BSI, pwn.watch, CVE.org, Msrc Update Guide

    0.4 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 32.8

    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
    87.61 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
    no public PoC known
    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
    9.8 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
    9.8
    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
    0.4 %
    Low — model estimates < 1% exploitation likelihood.
    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
    32.8
    Elevated — this CVE ranks above at least 10% of all CVEs scored today.
    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
    —
    Published

    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
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    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
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    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

    In the Linux kernel, the following vulnerability has been resolved: ipv4: free inet_opt and ireq_opt after an RCU grace period tcp_v4_syn_recv_sock() transfers ownership of ireq->ireq_opt to the child socket (newinet->inet_opt) without copying it. Another cpu can concurrently process a retransmitted SYN for the same request socket, and send a SYNACK from tcp_check_req(). tcp_v4_send_synack() and inet_csk_route_req() read ireq->ireq_opt under rcu_read_lock() only, and ip_build_and_send_pkt() and ip_options_build() then read opt->optlen twice. Note that the SYNACK timer itself is not an issue: it holds a reference on its request socket, and inet_csk_reqsk_queue_drop() calls timer_delete_sync() before the child can be freed. Since commit 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table"), request sockets are processed without holding the listener lock, so nothing prevents the child socket from being freed while the SYNACK is still being built. TCP child sockets do not have SOCK_RCU_FREE, and inet_sock_destruct() frees inet_opt with a plain kfree(), leading to a use-after-free in ip_options_build(). A similar issue exists with request socket migration (net.ipv4.tcp_migrate_req=1, or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE program). reqsk_timer_handler() clones the request socket with inet_reqsk_clone(), so that the old request socket and its clone share the same ireq_opt, then reqsk_migrate_reset() clears the pointer in the old one. Another cpu holding a reference on the old request socket can still be using these options (sending a SYNACK, or creating a child in tcp_v4_syn_recv_sock()) when the clone is freed, and tcp_v4_reqsk_destructor() also uses a plain kfree(). Readers already use RCU, and other paths replacing inet_opt (do_ip_setsockopt(), cipso_v4_sock_setattr()...) already use kfree_rcu(). Use kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor() as well. IPv6 is not affected by the first issue, because tcp_v6_syn_recv_sock() duplicates the options. tcp_v6_reqsk_destructor() has the same migration issue with ipv6_opt, which is only set by CALIPSO. This will be addressed in a separate patch.

    Source: Debian LTS Advisories, Debian Security Advisories, suse_csaf, BSI WID Portal, BSI CSAF, pwn.watch, cvelistv5, NVD (NIST), Microsoft Security Update Guide

    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
    LinuxLinux
    • 5.16 – < 6.1.190
    • 6.2 – < 6.6.159
    • 6.13 – < 6.18.56
    • 6.19 – < 7.2.10
    • 6.7 – < 6.12.113
    • —
    • 4.4 – < 5.10.272
    • 5.11 – < 5.15.223
    • 6.1.190
    • 6.6.159
    • 6.18.56
    • 7.2.10
    • 6.12.113
    • 7.3
    • 5.10.272
    • 5.15.223

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxtrixie
    Linuxdebianlinux-6.12bookworm

    References & sources

    • git.kernel.orgLinux stable fix commitpwn-watch
    • git.kernel.orgstable/c/26d4c36d318cffbbd160884a0e4cec0da4da4936
    • git.kernel.orgstable/c/742f73df544e03744f2981c467d6542fe8172a2a
    • git.kernel.orgstable/c/89b5b1eb7d633c33832b7ff2c02e19a144705036
    • git.kernel.orgstable/c/95a8c8fa9f27dce64c40c41c062de7728bf34ab5
    • git.kernel.orgstable/c/a47406c769f72c070386985488f1c4d057df86b2
    • git.kernel.orgstable/c/b3b027ef0cd322bfa839b9aaf5b27551eea54cf6
    • git.kernel.orgstable/c/e3f33b0a1d89d738e2b913dab519226eaf76e15b
    • pwn.watchpwn.watch: Linux kernel CVE-2026-98432: TCP use-after-free rated 9.8, Anthropic says its AI built a remote root exploitpwn-watch
    • NVD (NIST)NVD: CVE-2026-98432pwn-watch
    • OSV (Open Source Vulnerabilities)OSV: CVE-2026-98432 (fixed versions)pwn-watch
    • anthropic.comDiscovering and exploiting vulnerabilities in critical, real-world software with Claudepwn-watch
    • thehackernews.comAnthropic's Unreleased AI Model Chains Flaws Into Working Chrome, Safari, Windows and Linux Exploitspwn-watch
    • openwall.comlists/oss-security/2026/10/30/1
    • openwall.comGo Security Team: Protecting against CVE-2026-98432 (golang-announce, via oss-security)pwn-watch
    • thehackernews.comLinux Kernel TCP Flaw With 9.8 CVSS Score Affects Ubuntu, Red Hat and Other Distributionspwn-watch
    • openwall.comlists/oss-security/2026/10/30/6
    • github.comH1z3-br0/CVE-2026-98432: research toolkit (race trigger, use-after-free oracle, leak parser; no root stage)pwn-watch

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedCVE Program

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2026/10/30/6

      Source identifier: af854a3a-2127-422b-91ae-364da2661108

    2. Record modifiedCVE Program

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2026/10/30/1

      Source identifier: af854a3a-2127-422b-91ae-364da2661108

    3. Record modifiedLinux

      CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

      Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    4. Record modifiedLinux

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/98xxx/CVE-2026-98432.json">CVE-2026-98432</a>

      Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    5. ReceivedLinux

      Description added or changed

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      In the Linux kernel, the following vulnerability has been resolved: ipv4: free inet_opt and ireq_opt after an RCU grace period tcp_v4_syn_recv_sock() transfers ownership of ireq->ireq_opt to the child socket (newinet->inet_opt) without copying it. Another cpu can concurrently process a retransmitted SYN for the same request socket, and send a SYNACK from tcp_check_req(). tcp_v4_send_synack() and inet_csk_route_req() read ireq->ireq_opt under rcu_read_lock() only, and ip_build_and_send_pkt() and ip_options_build() then read opt->optlen twice. Note that the SYNACK timer itself is not an issue: it holds a reference on its request socket, and inet_csk_reqsk_queue_drop() calls timer_delete_sync() before the child can be freed. Since commit 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table"), request sockets are processed without holding the listener lock, so nothing prevents the child socket from being freed while the SYNACK is still being built. TCP child sockets do not have SOCK_RCU_FREE, and inet_sock_destruct() frees inet_opt with a plain kfree(), leading to a use-after-free in ip_options_build(). A similar issue exists with request socket migration (net.ipv4.tcp_migrate_req=1, or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE program). reqsk_timer_handler() clones the request socket with inet_reqsk_clone(), so that the old request socket and its clone share the same ireq_opt, then reqsk_migrate_reset() clears the pointer in the old one. Another cpu holding a reference on the old request socket can still be using these options (sending a SYNACK, or creating a child in tcp_v4_syn_recv_sock()) when the clone is freed, and tcp_v4_reqsk_destructor() also uses a plain kfree(). Readers already use RCU, and other paths replacing inet_opt (do_ip_setsockopt(), cipso_v4_sock_setattr()...) already use kfree_rcu(). Use kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor() as well. IPv6 is not affected by the first issue, because tcp_v6_syn_recv_sock() duplicates the options. tcp_v6_reqsk_destructor() has the same migration issue with ipv6_opt, which is only set by CALIPSO. This will be addressed in a separate patch.
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/98xxx/CVE-2026-98432.json">CVE-2026-98432</a>
      Referenceadded
      —
      https://git.kernel.org/stable/c/11a03ce3c4a62d84c10ccdfe47f8075006498568
      Referenceadded
      —
      https://git.kernel.org/stable/c/26d4c36d318cffbbd160884a0e4cec0da4da4936
      Referenceadded
      —
      https://git.kernel.org/stable/c/742f73df544e03744f2981c467d6542fe8172a2a
      Referenceadded
      —
      https://git.kernel.org/stable/c/89b5b1eb7d633c33832b7ff2c02e19a144705036
      Referenceadded
      —
      https://git.kernel.org/stable/c/95a8c8fa9f27dce64c40c41c062de7728bf34ab5
      Referenceadded
      —
      https://git.kernel.org/stable/c/a47406c769f72c070386985488f1c4d057df86b2
      Referenceadded
      —
      https://git.kernel.org/stable/c/b3b027ef0cd322bfa839b9aaf5b27551eea54cf6
      Referenceadded
      —
      https://git.kernel.org/stable/c/e3f33b0a1d89d738e2b913dab519226eaf76e15b

      Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Linked advisories

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