HighCVE-2026-109518

    APT RCE via hard link reuse (CVE-2026-109518)

    Published Last modified Sources: pwn.watch, BSI, CVE.org, Ubuntu, Debian, Debian LTS

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    What is affected, what to do

    On Debian, Ubuntu, and derivative Linux distributions, an on-path attacker who can manipulate the HTTP traffic (including a malicious mirror or proxy) between an APT client and an archive server triggered by a package install can trick the client into installing an attacker-controlled unverified package and achieve remote code execution with root privileges. The vulnerability is caused by the reuse of hard links and requires the client to follow redirects and retry the download of package files.

    Update Ubuntu APT to version 2.0.12+esm1, Debian APT to version 1.2.36, Debian APT to version 1.4.12.

    Affected
    • Ubuntu APT lt 2.0.0..2.0.12+esm1
    • Debian APT lt *..1.2.36
    • Debian APT lt 1.4.0..1.4.12
    • Debian APT lt 1.6.0..1.6.19
    • Debian APT lt 1.8.0..1.8.2.4
    • Debian APT lte 1.8.3..1.8.5
    • Debian APT lt 2.0.0..2.0.12
    • Debian APT lt 2.2.0..2.2.5
    • Debian APT lt 2.4.0..2.4.15
    • Debian APT lt 2.6.0..2.6.2
    • Debian APT lt 2.8.0..2.8.4
    • Debian APT lt 3.0.0..3.0.4
    • Debian APT lt 3.2.0..3.2.1
    • Debian APT lt 3.3.0..3.3.6
    • Ubuntu APT lt *..1.0.1ubuntu2.24+esm4
    • Ubuntu APT lt 1.2.0..1.2.36+esm1
    • Ubuntu APT lt 1.6.0..1.6.19+esm1
    • Ubuntu APT lt 2.4.0..2.4.15ubuntu0.1
    • Ubuntu APT lt 2.8.0..2.8.4ubuntu0.1
    • Ubuntu APT lt 3.2.0..3.2.1ubuntu0.1
    • Ubuntu APT lt 3.3.0..3.3.3ubuntu0.1
    Fixed in
    • Ubuntu APT 2.0.12+esm1
    • Debian APT 1.2.36
    • Debian APT 1.4.12
    • Debian APT 1.6.19
    • Debian APT 1.8.2.4
    • Debian APT 2.0.12
    • Debian APT 2.2.5
    • Debian APT 2.4.15
    • Debian APT 2.6.2
    • Debian APT 2.8.4
    • Debian APT 3.0.4
    • Debian APT 3.2.1
    • Debian APT 3.3.6
    • Ubuntu APT 1.0.1ubuntu2.24+esm4
    • Ubuntu APT 1.2.36+esm1
    • Ubuntu APT 1.6.19+esm1
    • Ubuntu APT 2.4.15ubuntu0.1
    • Ubuntu APT 2.8.4ubuntu0.1
    • Ubuntu APT 3.2.1ubuntu0.1
    • Ubuntu APT 3.3.3ubuntu0.1

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

    Metrics

    7.7

    Priority

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

    Source: Vendor (CNA), CVSS v4

    7.7

    CVSS v4

    Severity High on the scale from 0 to 10.

    Source: pwn.watch, BSI, CVE.org, Ubuntu, Debian, Debian LTS

    —

    EPSS score

    No value is available for this vulnerability.

    Show all metrics
    Severity
    High
    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
    68.50 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
    7.7 Methodology
    CVSS v4

    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
    7.7
    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
    CISA assessment (SSVC)
    Exploitation: none known · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 4 November 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-62, CWE-367

    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

    On Debian, Ubuntu, and derivative Linux distributions, an on-path attacker who can manipulate the HTTP traffic (including a malicious mirror or proxy) between an APT client and an archive server triggered by a package install can trick the client into installing an attacker-controlled unverified package and achieve remote code execution with root privileges. The vulnerability is caused by the reuse of hard links and requires the client to follow redirects and retry the download of package files. It requires the client to have a non-zero Acquire::Retries configuration setting; the value 3 is the default starting with Debian 12 (bookworm) and Ubuntu 22.04 LTS (Jammy Jellyfish), so older releases are unaffected in a default configuration

    Source: pwn.watch, BSI CSAF, BSI WID Portal, cvelistv5, NVD (NIST), Ubuntu Security Notices, CVE.org (MITRE), Debian Security Advisories, Debian LTS Advisories

    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
    DebianAPT
    • 3.2.0 – < 3.2.1
    • 1.4.0 – < 1.4.12
    • 1.6.0 – < 1.6.19
    • < 1.2.36
    • 1.8.3 – ≤ 1.8.5
    • 1.8.0 – < 1.8.2.4
    • 3.3.0 – < 3.3.6
    • 2.2.0 – < 2.2.5
    • 2.4.0 – < 2.4.15
    • 2.8.0 – < 2.8.4
    • 3.0.0 – < 3.0.4
    • 2.0.0 – < 2.0.12
    • 2.6.0 – < 2.6.2
    • 3.2.1
    • 1.4.12
    • 1.6.19
    • 1.2.36
    • —
    • 1.8.2.4
    • 3.3.6
    • 2.2.5
    • 2.4.15
    • 2.8.4
    • 3.0.4
    • 2.0.12
    • 2.6.2
    UbuntuAPT
    • 2.8.0 – < 2.8.4ubuntu0.1
    • < 1.0.1ubuntu2.24+esm4
    • 3.2.0 – < 3.2.1ubuntu0.1
    • 2.4.0 – < 2.4.15ubuntu0.1
    • 3.3.0 – < 3.3.3ubuntu0.1
    • 1.6.0 – < 1.6.19+esm1
    • 2.0.0 – < 2.0.12+esm1
    • 1.2.0 – < 1.2.36+esm1
    • 2.8.4ubuntu0.1
    • 1.0.1ubuntu2.24+esm4
    • 3.2.1ubuntu0.1
    • 2.4.15ubuntu0.1
    • 3.3.3ubuntu0.1
    • 1.6.19+esm1
    • 2.0.12+esm1
    • 1.2.36+esm1

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianaptbookworm
    Linuxdebianapttrixie
    Linuxubuntuaptbionic
    Linuxubuntuaptfocal
    Linuxubuntuaptjammy
    Linuxubuntuaptnoble
    Linuxubuntuaptresolute
    Linuxubuntuaptstonking
    Linuxubuntuapttrusty
    Linuxubuntuaptxenial

    Weakness classes (CWE)

    • CWE-62UNIX Hard Link

      Variant

      The product, when opening a file or directory, does not sufficiently account for when the name is associated with a hard link to a target that is outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

      Entry at MITRE CWE-62

    • CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition

      Base

      The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.

      Entry at MITRE CWE-367

    References & sources

    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 modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentremoved
      {"id":"CVE-2026-109518","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-11-04T17:34:16.834939Z"}
      —
      SSVC assessmentadded
      —
      {"id":"CVE-2026-109518","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-11-04T00:00:00+00:00"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    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/2026/11/04/12

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

    3. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-109518","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-11-04T17:34:16.834939Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    4. Receivedubuntu.com

      CVSS V4.0: AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

      Weakness type: CWE-367, CWE-62

      Description added or changed

      Show 7 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      On Debian, Ubuntu, and derivative Linux distributions, an on-path attacker who can manipulate the HTTP traffic (including a malicious mirror or proxy) between an APT client and an archive server triggered by a package install can trick the client into installing an attacker-controlled unverified package and achieve remote code execution with root privileges. The vulnerability is caused by the reuse of hard links and requires the client to follow redirects and retry the download of package files. It requires the client to have a non-zero Acquire::Retries configuration setting; the value 3 is the default starting with Debian 12 (bookworm) and Ubuntu 22.04 LTS (Jammy Jellyfish), so older releases are unaffected in a default configuration
      CVSSadded
      —
      AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
      Weakness type (CWE)added
      —
      CWE-367
      Weakness type (CWE)added
      —
      CWE-62
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/109xxx/CVE-2026-109518.json">CVE-2026-109518</a>
      Referenceadded
      —
      https://lists.debian.org/debian-security-announce/2026/msg00526.html
      Referenceadded
      —
      https://ubuntu.com/security/notices/USN-8996-1

      Source identifier: security@ubuntu.com

    5. Record modifiedCVE Program

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://lists.debian.org/debian-lts-announce/2026/11/msg00004.html

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

    Linked advisories

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