install: TOCTOU symlink race (unlink-then-create without O_EXCL) allows arbitrary file overwrite

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.3 · CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H

EPSS

• CVE-2026-35355: 0.12% estimated exploitation activity in the next 30 days; percentile 1.71 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

copyfile in install/src/install.rs removes the destination then recreates it by pathname via File::create / fs::copy without OEXCL/createnew. Between the unlink and the recreate, a local attacker with write access to the destination directory can drop in a symlink and redirect the write. Impact: when install runs privileged into an attacker-writable directory (staging/build paths), the race allows redirecting writes to arbitrary files and overwriting sensitive system files (/etc/passwd, /etc/shadow). Recommendation: create atomically with createnew/OEXCL and copy via the opened fd rather than reopening by path. Remediation: Acknowledged by Canonical; fixed in commit b5bbabc1. --- Reported by Zellic in the uutils coreutils Program Security Assessment (prepared for Canonical, Jan 20 2026), audited commit 3a07ffc5a9bd4c283e75afa548ba1f1957bad242. Finding 3.50. Credit: Zellic.

Published by the source

6 Jul 2026, 19:54 UTC

Last modified by the source

6 Jul 2026, 19:54 UTC

Source last checked

26 Oct 2026, 15:43 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-239g-2685-54x3

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# Patch Next advisory brief: CVE-2026-35355

Advisory: install: TOCTOU symlink race (unlink-then-create without O_EXCL) allows arbitrary file overwrite
IDs: CVE-2026-35355, GHSA-239g-2685-54x3
Record: https://patchnext.com/advisories/cve-2026-35355 (revision 1, source checked 26 Oct 2026, 15:43 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: uu_install 0.6.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io uu_install: affected < 0.6.0; fixed in 0.6.0

## Suggested inspection (read-only)
- crates.io uu_install: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on uu_install.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-239g-2685-54x3 (GitHub-reviewed advisory GHSA-239g-2685-54x3 lists affected ranges: crates.io uu_install >=0 <0.6.0)

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