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Fencer Intel
high 7.7

CVE-2026-109518 json

APT RCE via hard link reuse

published 5d ago modified 4d ago also EUVD-2026-116969

cvss
7.7
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 60%
public exploits
0
none known

Summary

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

Patch / fix

  • Debian APT 1.2.36, 1.4.12, 1.6.19, 1.8.2.4, 2.0.12, 2.2.5, 2.4.15, 2.6.2, 2.8.4, 3.0.4, 3.2.1, 3.3.6
  • Ubuntu APT 1.0.1ubuntu2.24+esm4, 1.2.36+esm1, 1.6.19+esm1, 2.0.12+esm1, 2.4.15ubuntu0.1, 2.8.4ubuntu0.1, 3.2.1ubuntu0.1, 3.3.3ubuntu0.1
  • apt Debian 12 2.6.2
  • apt Debian 13 3.0.4
  • apt Debian 14 3.3.6

debian advisories DEBIAN-CVE-2026-109518

  • apt Ubuntu 22.04 LTS 2.4.15ubuntu0.1
  • apt Ubuntu 24.04 LTS 2.8.4ubuntu0.1
  • apt Ubuntu 26.10 3.3.3ubuntu0.1
  • apt Ubuntu 26.04 LTS 3.2.1ubuntu0.1
  • apt Ubuntu Pro 14.04 LTS 1.0.1ubuntu2.24+esm4
  • apt Ubuntu Pro 16.04 LTS 1.2.36+esm1
  • apt Ubuntu Pro 18.04 LTS 1.6.19+esm1
  • apt Ubuntu Pro 20.04 LTS 2.0.12+esm1

ubuntu advisories UBUNTU-CVE-2026-109518

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • apt Alpine 3.24 3.2.1-r0

alpine advisories ALPINE-CVE-2026-109518

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Is CVE-2026-109518 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-109518 updated cvss 8.1

apt: apt: Remote code execution via hard link reuse during package download retries

  • Red Hat Hardened Images apt 3.3.5-2.hum1
    affected: workaround, no fix available

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
6d ago

Exploit prediction

0.93% chance of exploitation in the next 30 days, higher than 60% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 7.7 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 4.0 7.7 CVSS:4.0/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

Affected products

  • Debian APT
  • Ubuntu APT

Classification

Weakness
  • CWE-62 UNIX Hard Link
  • CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.