CVE-2026-35355Medium· 6.3▾ Sunlitinstall: TOCTOU symlink race (unlink-then-create without O_EXCL) allows arbitrary file overwrite
▾ Sunlit zone — Low / medium · no exploitation signal
impact 34.7 · likelihood 0 · exploitation 0
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Exploit-prediction probability, daily snapshots since Aug 1.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via GHSA
0.1%
copy_file in install/src/install.rs removes the destination then recreates it by pathname via File::create / fs::copy without O_EXCL/create_new. 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 create_new/O_EXCL 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.
uu_install < 0.6.0Upgrade to a patched release:
uu_install 0.6.0Connected by shared product, vendor, weakness, or advisory.
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