CVE-2026-41991 — Predictable Temporary File in GNU gzip

Affected: GNU gzip

GNU gzip contains a vulnerability in the gzexe utility related to insecure temporary file handling. When the mktemp utility is not available in the user’s PATH, gzexe falls back to constructing a temporary file path based solely on the process ID (PID). This predictable filename is created without exclusive access or existence checks. A local attacker can pre‑create the predicted temporary file path as a symbolic link pointing to an arbitrary file writable by the victim. When gzexe runs, it follows the symlink and overwrites the target file, resulting in a time‑of‑check to time‑of‑use (TOCTOU) condition that allows arbitrary file overwrite.

This issue has been fixed in the commit 4e6f8b24ab823146ab8776f0b7fe486ab34d4269

USN-8512-1 — gzip vulnerabilities

Affected: Ubuntu:22.04:LTS: gzip, Ubuntu:24.04:LTS: gzip, Ubuntu:26.04:LTS: gzip

It was discovered that Gzip's gzexe utility handled temporary files in an insecure manner. When the mktemp utility was not available, gzexe constructed a temporary file path based on the process ID, which could be predicted. A local attacker could possibly use this issue to overwrite arbitrary files via a symlink attack. (CVE-2026-41991)

It was discovered that Gzip incorrectly handled certain compressed files. An attacker could possibly use this issue to obtain sensitive information or cause Gzip to crash, resulting in a denial of service. (CVE-2026-41992)

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CVE-2026-41991 — Predictable Temporary File in GNU gzip

USN-8512-1 — gzip vulnerabilities