CVE-2026-6654: Double-Free / Use-After-Free (UAF) in the `IntoIter::drop` and `ThinVec::clear` functions in the thin_vec crat

Routine

MEDIUM 5.1DOWNGRADE

CVE-2026-6654 is a medium-severity flaw (CVSS 5.1) affecting thin-vec. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Double-Free / Use-After-Free (UAF) in the `IntoIter::drop` and `ThinVec::clear` functions in the thin_vec crate. A panic in `ptr::drop_in_place` skips setting the length to zero.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.1 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 94%)
CISA exploited list	No
Weakness	CWE-415, CWE-416, CWE-1341
Published	2026-04-20
Last modified	2026-10-26

Publisher (CNA): Mozilla Corporation · Vendor: mozilla

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-20 11:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

mozilla thin-vec DOWNGRADE

Affected: 0.2.15

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.2.15

1. Check installed version

apt-cache policy thin-vec || rpm -q thin-vec || thin-vec --version

2. No fixed release: DOWNGRADE to a release before 0.2.15 (Debian / Ubuntu)

apt-cache madison thin-vec sudo apt install thin-vec=<VERSION_BEFORE_0.2.15> sudo apt-mark hold thin-vec

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

dnf --showduplicates list thin-vec sudo dnf downgrade thin-vec-<VERSION_BEFORE_0.2.15> sudo dnf versionlock add thin-vec

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.

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-2026-6654?

thin-vec: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-6654 being exploited?

CVE-2026-6654 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-2026-6654 affect?

CVE-2026-6654 affects thin-vec. Severity is medium (CVSS 5.1). Double-Free / Use-After-Free (UAF) in the `IntoIter::drop` and `ThinVec::clear` functions in the thin_vec crate. A panic in `ptr::drop_in_place` skips setting the length to zero.

How urgent is CVE-2026-6654?

Priority 24/100. Public exploit reference

References

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