CVE-2026-18477: A TOCTOU (Time-of-Check Time-of-Use) vulnerability in GNU tar's incremental dumpdir 'X' rename handling allows

Routine

MEDIUM 4.4WATCHLISTDOWNGRADEDOWNGRADEMITIGATE

CVE-2026-18477 is a medium-severity flaw (CVSS 4.4) affecting tar, openshift container platform, enterprise linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 m

Why this priority

On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	4.4 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.1% (top 100%)
CISA exploited list	No
Weakness	CWE-367
Published	2026-08-03
Last modified	2026-09-22

Publisher (CNA): Red Hat, Inc. · Vendor: gnu · redhat

Last updated 2026-09-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-03 17:16 UTCPublished CVE record published
2026-09-22 22:17 UTCUpdated Record last modified

gnu tar DOWNGRADE

Affected: 1.35

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.35

1. Check installed version

apt-cache policy tar || rpm -q tar || tar --version

2. No fixed release: DOWNGRADE to a release before 1.35 (Debian / Ubuntu)

apt-cache madison tar sudo apt install tar=<VERSION_BEFORE_1.35> sudo apt-mark hold tar

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list tar sudo dnf downgrade tar-<VERSION_BEFORE_1.35> sudo dnf versionlock add tar

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

redhat openshift container platform DOWNGRADE

Affected: 4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.0

1. Check installed version

apt-cache policy openshift-container-platform || rpm -q openshift-container-platform || openshift-container-platform --version

2. No fixed release: DOWNGRADE to a release before 4.0 (Debian / Ubuntu)

apt-cache madison openshift-container-platform sudo apt install openshift-container-platform=<VERSION_BEFORE_4.0> sudo apt-mark hold openshift-container-platform

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list openshift-container-platform sudo dnf downgrade openshift-container-platform-<VERSION_BEFORE_4.0> sudo dnf versionlock add openshift-container-platform

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

redhat enterprise linux MITIGATE

Affected: 8.0 · 9.0 · 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-18477?

tar: downgrade or apply the listed mitigation; openshift container platform: downgrade or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-18477 being exploited?

CVE-2026-18477 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-18477 affect?

CVE-2026-18477 affects tar, openshift container platform, enterprise linux. Severity is medium (CVSS 4.4). 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

How urgent is CVE-2026-18477?

Priority 20/100. On your watchlist

Software pages

Red Hat OpenShift vulnerabilities

Related CVEs

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References

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