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Cross ImplementationApplication · Cross Crypto

CVE-2026-41509

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-08
Fix available
A fix is available. Upgrade to 2026-03-23 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A buffer overflow vulnerability exists in the CROSS post-quantum signature library's crypto_sign_open() function. The issue is caused by an integer underflow of the mlen (message length) variable, which can lead to memory corruption during signature verification.

MitigationUpgrade to the latest version of the CROSS library after commit fc6b7e7, which contains the patch fixing the mlen underflow that causes the buffer overflow in crypto_sign_open().

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Cross ImplementationApplication
Affected:< 2026-03-23

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Locate the CROSS library installation
    Search for libcross-crypto, libcross, or CROSS library files in the system (e.g., find /usr -name '*cross*' -o -name '*CROSS*' 2>/dev/null, or check project dependencies in package managers, build files, or container images)
    Affected if The CROSS library is present in the environment
  2. Identify the CROSS library version
    Check the library version via its metadata: examine the shared object (objdump -p libname.so | grep -i version), check the package manager (dpkg -l, rpm -qi, pip show), review the source code tags, or inspect the build artifacts for version information
    Affected if The version cannot be determined or is earlier than the 2026-03-23 release
  3. Verify the installed version against affected range
    Compare the found version to the affected range: any version dated or released before March 23, 2026 is vulnerable
    Affected if The installed version is < 2026-03-23 or the version date is unknown/earlier
  4. Check for usage of crypto_sign_open()
    Search codebase for calls to crypto_sign_open() function: grep -r 'crypto_sign_open' source_files/ or inspect binary for symbols (nm -D binary | grep crypto_sign_open)
    Affected if The application or service uses crypto_sign_open() for signature verification

The environment is affected if the CROSS library version is earlier than 2026-03-23 AND the crypto_sign_open() function is being used for signature verification.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2026-03-23 or later
Fixed in 2026-03-23
Vendor patch github.com →
Interim mitigation

Upgrade to the latest version of the CROSS library after commit fc6b7e7, which contains the patch fixing the mlen underflow that causes the buffer overflow in crypto_sign_open().

Recommended fix High confidence

Upgrade to commit fc6b7e78cdf789bb5c395a81dc601356f1383da0 or any later version/branch containing this fix (2026-03-23 or later)

  1. 1. Identify the current version of CROSS-implementation in use by checking the git commit hash or version file
  2. 2. Ensure the current version is prior to commit fc6b7e78cdf789bb5c395a81dc601356f1383da0 (before 2026-03-23)
  3. 3. Update the repository to the fixed commit by running: git fetch origin
  4. 4. Check out or merge the fixed commit: git checkout fc6b7e78cdf789bb5c395a81dc601356f1383da0, or pull latest and ensure the fix is included
  5. 5. Rebuild the library/application with the updated code
  6. 6. Verify the fix by reviewing the changes in commit fc6b7e78cdf789bb5c395a81dc601356f1383da0 to confirm the mlen underflow patch is applied
  7. 7. Test the crypto_sign_open() function to ensure it handles signatures correctly without buffer overflow

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Cross Implementation Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-41509 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data