CVE-2026-6330: The ML-KEM ARM64 NEON ciphertext comparison only compares half of the input, breaking the Fujisaki-Okamoto tra

Routine

MEDIUM 6.5REMOTEUPGRADE

CVE-2026-6330 is a medium-severity flaw (CVSS 6.5) affecting wolfssl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The ML-KEM ARM64 NEON ciphertext comparison only compares half of the input, breaking the Fujisaki-Okamoto transform's implicit rejection and weakening IND-CCA2 security on that code path. The constant-time comparison effectively ignored part of the re-encrypted ciphertext, so a decapsulating party could fail to detect a manipulated ciphertext and proceed without the standard's required implicit rejection.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 94%)
CISA exploited list	No
Weakness	CWE-327
Published	2026-06-25
Last modified	2026-06-27

Publisher (CNA): wolfSSL Inc. · Vendor: wolfssl

Last updated 2026-06-27 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-25 22:17 UTCPublished CVE record published
2026-06-27 19:50 UTCUpdated Record last modified

wolfssl wolfssl UPGRADE

Affected: >= 5.7.4 and < 5.9.2

Fixed in: 5.9.2

Safe to downgrade to: a release before 5.7.4

1. Check installed version

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

2. UPGRADE to 5.9.2 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade wolfssl

Note

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

3. If no update is available yet, DOWNGRADE to a release before 5.7.4 (Debian / Ubuntu)

apt-cache madison wolfssl sudo apt install wolfssl=<VERSION_BEFORE_5.7.4> sudo apt-mark hold wolfssl

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list wolfssl sudo dnf downgrade wolfssl-<VERSION_BEFORE_5.7.4> sudo dnf versionlock add wolfssl

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-2026-6330?

wolfssl: upgrade to 5.9.2. Exact commands for each OS are on this page.

Is CVE-2026-6330 being exploited?

CVE-2026-6330 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-2026-6330 affect?

CVE-2026-6330 affects wolfssl. Severity is medium (CVSS 6.5). The ML-KEM ARM64 NEON ciphertext comparison only compares half of the input, breaking the Fujisaki-Okamoto transform's implicit rejection and weakening IND-CCA2 security on that code path. The constant-time comparison effectively ignored pa

How urgent is CVE-2026-6330?

Priority 29/100. Remotely exploitable, no login, no user action

Software pages

wolfSSL vulnerabilities

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References

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