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GNU tar CVE-2026-18477

| EUVDEUVD-2026-52336 MEDIUM
Time-of-check Time-of-use (TOCTOU) Race Condition (CWE-367)
2026-08-03 redhat GHSA-v7fx-gjvh-347c
Privilege Escalation Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 6 Red Hat Enterprise Linux 7 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 9 Red Hat Openshift Container Platform 4 Red Hat Hardened Images Red Hat
4.4
CVSS 3.1 · Vendor: redhat
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Severity by source

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

Local-only vector with race-condition complexity; write access and admin-initiated restore required; pure integrity impact with no confidentiality or availability consequences.

3.1 AV:L/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:N
4.0 AV:L/AC:H/AT:P/PR:L/UI:A/VC:N/VI:H/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
High
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

Lifecycle Timeline

2
Analysis Generated
Aug 03, 2026 - 17:13 vuln.today
CVE Published
Aug 03, 2026 - 15:34 cve.org
MEDIUM 4.4

DescriptionCVE.org

A TOCTOU (Time-of-Check Time-of-Use) vulnerability in GNU tar's incremental dumpdir 'X' rename handling allows a local attacker with write access to a directory being backed up to influence the restore process if the attacker has access to the system where the restore is being performed. During restoration, files or directories may be created, renamed or overwritten outside the intended extraction directory. This could lead to unauthorized file modification or, in some cases, privilege escalation. Exploitation does not require the attacker to modify or craft the archive, and standard backup and restore workflows-including extracting into a newly created directory without using the -P option do not mitigate the issue.

AnalysisAI

GNU tar's incremental restore path contains a TOCTOU race condition in dumpdir 'X' rename handling, allowing a local attacker with write access to a backed-up directory to redirect file operations outside the intended extraction root during a privileged restore. Successful exploitation can result in arbitrary file creation, rename, or overwrite - enabling privilege escalation on systems running Red Hat Enterprise Linux 6 through 10 and Red Hat Hardened Images. No public exploit is identified at time of analysis, and no CISA KEV listing exists; the CVSS score of 4.4 reflects the constrained attack prerequisites including a required race window and administrator-initiated restore.

Technical ContextAI

GNU tar's incremental backup mode (invoked with --listed-incremental or -g) records filesystem state in a dumpdir format, using 'X' markers to encode file rename operations. During restoration, tar processes these rename entries sequentially - checking the source path and then performing the rename. CWE-367 (Time-of-Check Time-of-Use) describes exactly this pattern: the window between the check and the use allows an attacker to swap in a symlink or manipulate directory entries, causing tar to follow attacker-controlled paths outside the extraction root. The vulnerability is present in GNU tar as packaged across Red Hat Enterprise Linux 6, 7, 8, 9, and 10, as well as Red Hat Hardened Images and OpenShift Container Platform 4, per CPE data (cpe:2.3:a:red_hat:red_hat_enterprise_linux_*). The underlying flaw resides in upstream GNU tar's incremental restore logic, but the advisory scope and CPEs are Red Hat-specific.

RemediationAI

Apply Red Hat security errata for the affected RHEL versions once published - monitor https://access.redhat.com/security/cve/CVE-2026-18477 for the official update package. No specific fixed GNU tar version or RHSA advisory number was confirmed in the available data at time of analysis; track https://bugzilla.redhat.com/show_bug.cgi?id=2509735 for patch status updates. As a compensating control, restrict write access to directories included in incremental backup sets to only fully trusted accounts, eliminating the attacker's ability to manipulate the backup source before or during restoration. Additionally, perform restore operations in isolated environments under a dedicated backup service account that holds no additional system privileges, reducing the impact of any path traversal. Critically, the CVE description explicitly states that standard defenses - extracting into a newly created directory and omitting the -P flag - do NOT mitigate this vulnerability, so do not rely on these controls as substitutes for patching.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SLES15-SP5-CHOST-BYOS-SAP-CCloud Affected
SLES15-SP6-CHOST-BYOS Affected
SLES15-SP6-CHOST-BYOS-Aliyun Affected
SLES15-SP6-CHOST-BYOS-Azure Affected
SLES15-SP6-CHOST-BYOS-EC2 Affected

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CVE-2026-18477 vulnerability details – vuln.today
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