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High, CVSS 8.2amended

Auto-Reseeding HMAC-DRBG could panic for some output lengths

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (libcrux-hmac-drbg 0.0.2), 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.

The automatically reseeding implementations of HMAC-DRBG would panic if called with a desired non-zero output length cleanly divisible by `65_536`, the maximum number of output bytes that can be generated before reseeding has to happen.

Impact An application relying on `libcrux-hmac-drgb` to provide randomness of byte length a non-zero integer multiple of `65_536` in a single call to `fill_bytes` would panic. Any calls with output buffer lengths not cleanly divisible by `65_536` are not affected.

Mitigation With release the release of version `0.0.2` of `libcrux-hmac-drbg` this bug has been fixed and reseeding DRBG implementations can be used with arbitrary output lengths. We recommend users upgrade to `libcrux-hmac-drbg` version `0.0.2`.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  2. Revision 1 · created ·

    Published from osv record RUSTSEC-2026-0329

Agent brief

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# Patch Next advisory brief: rustsec-2026-0329

Advisory: Auto-Reseeding HMAC-DRBG could panic for some output lengths
IDs: rustsec-2026-0329
Record: https://patchnext.com/advisories/rustsec-2026-0329 (revision 2, source checked 25 Oct 2026, 04:53 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-hmac-drbg 0.0.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io libcrux-hmac-drbg: affected >= 0.0.0-0, < 0.0.2; fixed in 0.0.2

## Suggested inspection (read-only)
- crates.io libcrux-hmac-drbg: 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-hmac-drbg.
- 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://osv.dev/vulnerability/RUSTSEC-2026-0329 (OSV record RUSTSEC-2026-0329 lists affected ranges: crates.io libcrux-hmac-drbg >=0.0.0-0 <0.0.2 (fixed))

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