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GNU tar CVE-2026-18508

| EUVDEUVD-2026-52327 MEDIUM
Improper Link Resolution Before File Access (CWE-59)
2026-08-03 redhat GHSA-4f5j-wqjr-hx49
4.4
CVSS 3.1 · Vendor: redhat
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Severity by source

Vendor (redhat) PRIMARY
4.4 MEDIUM
AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
vuln.today AI
3.6 LOW

AC:H reflects the required preexisting symlink prerequisite beyond attacker control; all other metrics align with the provided vector.

3.1 AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
4.0 AV:L/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
SUSE
MEDIUM
qualitative
Red Hat
4.4 MEDIUM
qualitative

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

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

Lifecycle Timeline

2
Analysis Generated
Aug 03, 2026 - 15:51 vuln.today
CVE Published
Aug 03, 2026 - 14:51 cve.org
MEDIUM 4.4

DescriptionCVE.org

A flaw was found in GNU tar. When extracting an archive with the --one-top-level option, hardlink targets are not confined to the designated top-level directory and may resolve relative to the extraction working directory. A crafted archive can create hardlinks that escape the intended boundary and, when combined with a preexisting symbolic link under the working directory, may allow writing outside that boundary during a single extraction.

AnalysisAI

GNU tar's --one-top-level extraction mode fails to confine hardlink targets to the designated top-level directory, allowing a crafted archive to plant hardlinks that escape the intended extraction boundary. When combined with a preexisting symbolic link already present under the working directory, an attacker who can induce a victim to extract a malicious archive may read or write files outside the intended extraction scope on systems running affected RHEL versions (6 through 10) and Red Hat Hardened Images. No public exploit has been identified at time of analysis, and exploitation requires both user interaction and a specific environmental pre-condition, keeping real-world risk moderate despite GNU tar's ubiquitous deployment.

Technical ContextAI

CWE-59 (Improper Link Resolution Before File Access, 'Link Following') describes the root cause: GNU tar's implementation of --one-top-level enforces boundary checks for regular files but fails to apply equivalent confinement logic to hardlink targets. Hardlinks in a tar archive reference inode paths that, when resolved, are computed relative to the current working directory rather than the designated top-level extraction directory. This means an attacker-controlled archive can embed hardlink entries whose targets traverse upward or sideways from the extraction root. The secondary condition - a preexisting symbolic link under the working directory - allows the hardlink traversal to chain through that symlink, reaching filesystem locations entirely outside the extraction scope in a single extraction pass. The affected CPE strings cover Red Hat Enterprise Linux 6 through 10 (cpe:2.3:a:red_hat:red_hat_enterprise_linux_{6-10}) and Red Hat Hardened Images, confirming the vulnerability is present in GNU tar as shipped in the RHEL ecosystem.

RemediationAI

Monitor the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-18508 and apply the GNU tar package update for the relevant RHEL version (6, 7, 8, 9, 10, or Hardened Images) as soon as it is released - exact patched package versions are not yet confirmed in the available intelligence. As a compensating control prior to patching, avoid using the --one-top-level flag when extracting archives from untrusted sources; extracting into an isolated, empty directory (with no symlinks) under a dedicated unprivileged account limits the blast radius. If automated pipelines extract archives with --one-top-level, audit the working directory for preexisting symbolic links and remove or restrict them, noting that this may affect legitimate workflows relying on those symlinks.

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Vendor StatusVendor

SUSE

Severity: Moderate
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CVE-2026-18508 vulnerability details – vuln.today

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