openmls has improper tag validation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.1 · CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:H/VA:L/SC:L/SI:H/SA:L · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Membership and confirmation tags may not be checked correctly due to a missing length check. Any tag that is shorter than the expected tag, but matches up to its length, as well as any empty tag is considered valid. Impact The vulnerability affects a secondary authentication guarantee that MLS provides in certain scenarios. The primary authentication guarantee for all messages comes from the signature on MLS messages. This guarantee is not affected by the vulnerability. The secondary authentication attests to the group membership of the message author. For MLS private messages, it is implied in the AEAD. For MLS public messages, it is expressed as the ‘membership tag’, a MAC whose key is derived from the private group state only known to group members. In addition, for public Commit messages, the ‘confirmation tag’ works in a similar manner. Its purpose is to help members who processed the Commit message to ascertain that they now have the same view on the group as the creator of the…

Published by the source

4 Feb 2026, 20:24 UTC

Last modified by the source

4 Feb 2026, 20:24 UTC

Source last checked

26 Oct 2026, 15:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-8x3w-qj7j-gqhf

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# Patch Next advisory brief: GHSA-8x3w-qj7j-gqhf

Advisory: openmls has improper tag validation
IDs: GHSA-8x3w-qj7j-gqhf
Record: https://patchnext.com/advisories/ghsa-8x3w-qj7j-gqhf (revision 1, source checked 26 Oct 2026, 15:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: openmls 0.7.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io openmls: affected < 0.7.2; fixed in 0.7.2

## Suggested inspection (read-only)
- crates.io openmls: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on openmls.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-8x3w-qj7j-gqhf (GitHub-reviewed advisory GHSA-8x3w-qj7j-gqhf lists affected ranges: crates.io openmls >=0 <0.7.2)

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