CVE-2026-56391: GNU coreutils uniq is vulnerable to an out‑of‑bounds read due to incorrect handling of multibyte input when th

Q: How do I fix CVE-2026-56391?

coreutils: upgrade to newer than 9.11. Exact commands for each OS are on this page.

Q: Is CVE-2026-56391 being exploited?

CVE-2026-56391 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-56391 affect?

CVE-2026-56391 affects coreutils. Severity is medium (CVSS 6.1). GNU coreutils uniq is vulnerable to an out‑of‑bounds read due to incorrect handling of multibyte input when the -w (--check-chars) option is used. The find_field() function miscalculates the byte length of characters by repeatedly processin

Q: How urgent is CVE-2026-56391?

Priority 23/100. No elevated risk signals yet.

Routine

MEDIUM 6.1UPGRADE

CVE-2026-56391 is a medium-severity flaw (CVSS 6.1) affecting coreutils. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

GNU coreutils uniq is vulnerable to an out‑of‑bounds read due to incorrect handling of multibyte input when the -w (--check-chars) option is used. The find_field() function miscalculates the byte length of characters by repeatedly processing a fixed pointer instead of advancing through the input, resulting in an inflated length value. This incorrect length is later used in a memcmp operation, causing reads beyond the allocated buffer when proces

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 94%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-07-24
Last modified	2026-10-24

Publisher (CNA): CERT.PL · Vendor: gnu

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-24 09:16 UTCPublished CVE record published
2026-10-24 13:10 UTCUpdated Record last modified

gnu coreutils UPGRADE

Affected: >= 9.5 and <= 9.11

Fixed in: newer than 9.11

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 9.11 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade coreutils

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade coreutils

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Advisories and coverage

Official advisories

CERT Polska: Vulnerabilities in GNU coreutils software 2026-07-24

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-2026-56391?

coreutils: upgrade to newer than 9.11. Exact commands for each OS are on this page.

Is CVE-2026-56391 being exploited?

CVE-2026-56391 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-2026-56391 affect?

CVE-2026-56391 affects coreutils. Severity is medium (CVSS 6.1). GNU coreutils uniq is vulnerable to an out‑of‑bounds read due to incorrect handling of multibyte input when the -w (--check-chars) option is used. The find_field() function miscalculates the byte length of characters by repeatedly processin

How urgent is CVE-2026-56391?

Priority 23/100. No elevated risk signals yet.

Related CVEs

CVE-2026-56392 MEDIUM 6.1 MITIGATE GNU coreutils unexpand is vulnerable to a heap-based buffer overflow due to an integer overflow during buffer

References

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