Predictable Temporary File in GNU gzip

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Summary

CVECVE-2026-41991
StatePUBLISHED
AssignerCERT-PL
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-29 12:16:29 UTC
Updated2026-07-01 14:02:24 UTC
DescriptionGNU 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

Risk And Classification

Primary CVSS: v4.0 2 LOW from [email protected]

CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/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

EPSS: 0.001050000 probability, percentile 0.013050000 (date 2026-07-03)

Problem Types: CWE-377 | CWE-377 CWE-377: Insecure Temporary File

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary2LOWCVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/C...
4.0CNACVSS2LOWCVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
3.1[email protected]Primary4.7MEDIUMCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

CVSS v4.0 Breakdown

Attack Vector
Local
Attack Complexity
High
Attack Requirements
Present
Privileges Required
None
User Interaction
Passive
Confidentiality
None
Integrity
Low
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/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

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Gnu Gzip All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA GNU Gzip affected 1.14 semver Not specified

References

ReferenceSourceLinkTags
www.gnu.org/software/gzip [email protected] www.gnu.org Product
cert.pl/en/posts/2026/04/CVE-2026-41991 [email protected] cert.pl Broken Link
cgit.git.savannah.gnu.org/cgit/gzip.git/commit [email protected] cgit.git.savannah.gnu.org Patch
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Michał Majchrowicz (AFINE) (en)

CNA: Marcin Wyczechowski (AFINE) (en)

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