Plonky3 MultiField32Challenger: transcript malleability and challenge entropy loss

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-46654: 0.11% estimated exploitation activity in the next 30 days; percentile 1.20 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact - Key: challenger/src/multifieldchallenger.rs | MultiField32Challenger::duplexing | transcriptmalleability - Affected files: challenger/src/multifieldchallenger.rs, field/src/helpers.rs - Violated invariant: The Fiat-Shamir sponge must bind challenges to the exact sequence of observed field elements. Specifically: (1) absorption must be injective — distinct observation streams must produce distinct sponge states, (2) squeezing must be injective — distinct PF rate cells must yield distinct F challenge sequences, and (3) all bits of each absorbed PF element must influence the sponge state. - Exploit scenario: An attacker controlling prover-side observations can craft distinct transcripts that produce identical challenges, breaking the binding property of Fiat-Shamir. Three independent attack vectors exist: 1. Partial-chunk aliasing (absorb): duplexing() packs inputbuffer.chunks(numfelms) via reduce32 (base 2^32) with no length marker and no zeroing of unused rate slots.…

Published by the source

21 May 2026, 20:24 UTC

Last modified by the source

11 Jun 2026, 14:05 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-vj64-rjf3-w3v7

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# Patch Next advisory brief: CVE-2026-46654

Advisory: Plonky3 MultiField32Challenger: transcript malleability and challenge entropy loss
IDs: CVE-2026-46654, GHSA-vj64-rjf3-w3v7
Record: https://patchnext.com/advisories/cve-2026-46654 (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 8.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: p3-challenger 0.5.3, 0.4.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io p3-challenger: affected < 0.4.3; >= 0.5.0, < 0.5.3; fixed in 0.4.3, 0.5.3

## Suggested inspection (read-only)
- crates.io p3-challenger: 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 p3-challenger.
- 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-vj64-rjf3-w3v7 (GitHub-reviewed advisory GHSA-vj64-rjf3-w3v7 lists affected ranges: crates.io p3-challenger >=0 =0.5.0 <0.5.3)

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