CVE-2026-41509: CROSS implementation contains reference and optimized implementations of the CROSS post-quantum signature algo

Q: How do I fix CVE-2026-41509?

cross-implementation: upgrade to 2026-03-23. Exact commands for each OS are on this page.

Q: Is CVE-2026-41509 being exploited?

CVE-2026-41509 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-2026-41509 affect?

CVE-2026-41509 affects cross-implementation. Severity is critical (CVSS 9.8). CROSS implementation contains reference and optimized implementations of the CROSS post-quantum signature algorithm. Prior to commit fc6b7e7, there is a buffer overflow in crypto_sign_open() caused by an underflow of the integer mlen. This

Q: How urgent is CVE-2026-41509?

Priority 46/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-41509 is a critical-severity flaw (CVSS 9.8) affecting cross-implementation. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

CROSS implementation contains reference and optimized implementations of the CROSS post-quantum signature algorithm. Prior to commit fc6b7e7, there is a buffer overflow in crypto_sign_open() caused by an underflow of the integer mlen. This issue has been patched via commit fc6b7e7.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 73%)
CISA exploited list	No
Weakness	CWE-121, CWE-122
Published	2026-05-08
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: cross-crypto

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

Am I affected?

Timeline

2026-05-08 14:16 UTCPublished CVE record published
2026-10-26 19:10 UTCUpdated Record last modified

cross-crypto cross-implementation UPGRADE

Affected: < 2026-03-23

Fixed in: 2026-03-23

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy cross-implementation || rpm -q cross-implementation || cross-implementation --version

2. UPGRADE to 2026-03-23 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cross-implementation

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cross-implementation

Note

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

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-2026-41509?

cross-implementation: upgrade to 2026-03-23. Exact commands for each OS are on this page.

Is CVE-2026-41509 being exploited?

CVE-2026-41509 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-2026-41509 affect?

CVE-2026-41509 affects cross-implementation. Severity is critical (CVSS 9.8). CROSS implementation contains reference and optimized implementations of the CROSS post-quantum signature algorithm. Prior to commit fc6b7e7, there is a buffer overflow in crypto_sign_open() caused by an underflow of the integer mlen. This

How urgent is CVE-2026-41509?

Priority 46/100. Critical severity; Remotely exploitable, no login, no user action

References

← Back to latest CVEs