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High, CVSS 8.2

libcrux: Potential Panic on Overlong Ciphertext Buffer

GHSA-hc3c-63hc-2r9f

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (libcrux-chacha20poly1305 0.0.8), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.2 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

An application that passes in a ciphertext buffer of length greater than ptxt.len() + TAGLEN to libcruxchacha20poly1305::encrypt or libcruxchacha20poly1305::xchacha20poly1305::encrypt would experience a panic. Impact An application where the length of the ciphertext buffer is under attacker control could be made to crash. Mitigation The fix makes it so that libcruxchacha20poly1305::encrypt and libcruxchacha20poly1305::xchacha20poly1305::encrypt no longer panic in this case, but instead write out the ciphertext and tag into the first ptxt.len() + TAGLEN bytes of the provided buffer.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-hc3c-63hc-2r9f

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-hc3c-63hc-2r9f

Advisory: libcrux: Potential Panic on Overlong Ciphertext Buffer
IDs: GHSA-hc3c-63hc-2r9f
Record: https://patchnext.com/advisories/ghsa-hc3c-63hc-2r9f (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: libcrux-chacha20poly1305 0.0.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io libcrux-chacha20poly1305: affected < 0.0.8; fixed in 0.0.8

## Suggested inspection (read-only)
- crates.io libcrux-chacha20poly1305: 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 libcrux-chacha20poly1305.
- 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-hc3c-63hc-2r9f (GitHub-reviewed advisory GHSA-hc3c-63hc-2r9f lists affected ranges: crates.io libcrux-chacha20poly1305 >=0 <0.0.8)

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