Vulnerability-Lookup

CVE-2026-46654 (GCVE-0-2026-46654)

Vulnerability from cvelistv5 – Published: 2026-06-10 20:06 – Updated: 2026-06-11 14:01

Title

Plonky3 MultiField32Challenger: transcript malleability and challenge entropy loss

Summary

Plonky3 is a toolkit for polynomial IOPs (PIOPs). Prior to versions 0.4.3 and 0.5.3, an attacker controlling prover-side observations can craft distinct transcripts that produce identical challenges, breaking the binding property of Fiat-Shamir. This issue has been patched in versions 0.4.3 and 0.5.3.

Severity

8.9 (High)


                        
                          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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-11 14:01 UTC

CWE

CWE-1240 - Use of a Cryptographic Primitive with a Risky Implementation
CWE-345 - Insufficient Verification of Data Authenticity

Assigner

GitHub_M mitre root

References

1 reference

URL	Tags
https://github.com/Plonky3/Plonky3/security/advis…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version	CPE status
Plonky3	Plonky3	Affected: < 0.4.3 Affected: >= 0.5.0, < 0.5.3	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-46654

Vulnerability from fkie_nvd - Published: 2026-06-10 22:16 - Updated: 2026-07-23 09:10

Severity

8.9 (High) - 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

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/Plonky3/Plonky3/security/advisories/GHSA-vj64-rjf3-w3v7

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "Plonky3",
          "vendor": "Plonky3",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.4.3"
            },
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    },
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      "lang": "es",
      "value": "Plonky3 es un conjunto de herramientas para IOPs polinomiales (PIOPs). Antes de las versiones 0.4.3 y 0.5.3, un atacante que controle las observaciones del lado del probador puede elaborar transcripciones distintas que produzcan desaf\u00edos id\u00e9nticos, rompiendo la propiedad de enlace de Fiat-Shamir. Este problema ha sido parcheado en las versiones 0.4.3 y 0.5.3."
    }
  ],
  "id": "CVE-2026-46654",
  "lastModified": "2026-07-23T09:10:00.113",
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GHSA-VJ64-RJF3-W3V7

Vulnerability from github – Published: 2026-05-21 20:24 – Updated: 2026-06-11 14:05

Summary

Plonky3 MultiField32Challenger: transcript malleability and challenge entropy loss

Details

Impact

Key: challenger/src/multi_field_challenger.rs | MultiField32Challenger::duplexing | transcript_malleability
Affected files: challenger/src/multi_field_challenger.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:
Partial-chunk aliasing (absorb): duplexing() packs input_buffer.chunks(num_f_elms) via reduce_32 (base 2^32) with no length marker and no zeroing of unused rate slots. Observing [x] followed by a sample yields the same sponge state as [x, 0, ..., 0] (padded to num_f_elms) followed by a sample, since reduce_32 treats missing high limbs identically to explicit zeros. The attacker can extend or truncate the tail of any observation batch without changing future challenges.
Non-injective squeeze (squeeze): split_32 decomposes each PF rate cell into base-2^64 digits and maps each through TF::from_u64, which reduces mod F::ORDER (~2^31). Two distinct PF values whose base-2^64 digits differ only in their upper 33 bits produce identical F challenge sequences. This weakens the entropy of sampled challenges and can enable selective forgery when the attacker can influence the sponge state pre-squeeze.
High-bit truncation (observe Hash/MerkleCap): num_f_elms = PF::bits() / 64 computes the number of F limbs per PF element. For BN254 (254-bit field), this yields 3 limbs covering 192 bits — the top 62 bits of every digest word are silently discarded. An attacker can find two distinct BN254 hash digests that differ only in bits 192–253 and observe them interchangeably without affecting challenges.
Evidence: In duplexing(), the absorb path (reduce_32 with base 2^32) and the squeeze path (split_32 with base 2^64) use incompatible radices with no length domain separation. reduce_32 is a plain Horner fold acc * 2^32 + digit with no padding or tag, so trailing zeros are free. split_32 extracts u64 digits and casts each via TF::from_u64, which performs modular reduction, collapsing the top bits. The limb count PF::bits() / 64 is a floor division that silently drops all bits beyond 64 * num_f_elms for fields whose bit-width is not a multiple of 64.

Patches

Included in v0.4.3 and v0.5.3

Severity

8.9 (High)


                  
                    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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "p3-challenger"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
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            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "p3-challenger"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.5.0"
            },
            {
              "fixed": "0.5.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-46654"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1240",
      "CWE-345"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-21T20:24:21Z",
    "nvd_published_at": "2026-06-10T22:16:59Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\n- **Key**: `challenger/src/multi_field_challenger.rs` | `MultiField32Challenger::duplexing` | `transcript_malleability`\n- **Affected files**: `challenger/src/multi_field_challenger.rs`, `field/src/helpers.rs`\n- **Violated invariant**: The Fiat-Shamir sponge must bind challenges to the exact sequence of observed field elements. Specifically: (1) absorption must be injective \u2014 distinct observation streams must produce distinct sponge states, (2) squeezing must be injective \u2014 distinct PF rate cells must yield distinct F challenge sequences, and (3) all bits of each absorbed PF element must influence the sponge state.\n\n- **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:\n\n  1. **Partial-chunk aliasing (absorb)**: `duplexing()` packs `input_buffer.chunks(num_f_elms)` via `reduce_32` (base 2^32) with no length marker and no zeroing of unused rate slots. Observing `[x]` followed by a sample yields the same sponge state as `[x, 0, ..., 0]` (padded to `num_f_elms`) followed by a sample, since `reduce_32` treats missing high limbs identically to explicit zeros. The attacker can extend or truncate the tail of any observation batch without changing future challenges.\n\n  2. **Non-injective squeeze (squeeze)**: `split_32` decomposes each PF rate cell into base-2^64 digits and maps each through `TF::from_u64`, which reduces mod `F::ORDER` (~2^31). Two distinct PF values whose base-2^64 digits differ only in their upper 33 bits produce identical F challenge sequences. This weakens the entropy of sampled challenges and can enable selective forgery when the attacker can influence the sponge state pre-squeeze.\n\n  3. **High-bit truncation (observe Hash/MerkleCap)**: `num_f_elms = PF::bits() / 64` computes the number of F limbs per PF element. For BN254 (254-bit field), this yields 3 limbs covering 192 bits \u2014 the top 62 bits of every digest word are silently discarded. An attacker can find two distinct BN254 hash digests that differ only in bits 192\u2013253 and observe them interchangeably without affecting challenges.\n\n- **Evidence**: In `duplexing()`, the absorb path (`reduce_32` with base 2^32) and the squeeze path (`split_32` with base 2^64) use incompatible radices with no length domain separation. `reduce_32` is a plain Horner fold `acc * 2^32 + digit` with no padding or tag, so trailing zeros are free. `split_32` extracts u64 digits and casts each via `TF::from_u64`, which performs modular reduction, collapsing the top bits. The limb count `PF::bits() / 64` is a floor division that silently drops all bits beyond `64 * num_f_elms` for fields whose bit-width is not a multiple of 64.\n\n### Patches\n\nIncluded in v0.4.3 and v0.5.3",
  "id": "GHSA-vj64-rjf3-w3v7",
  "modified": "2026-06-11T14:05:27Z",
  "published": "2026-05-21T20:24:21Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Plonky3/Plonky3/security/advisories/GHSA-vj64-rjf3-w3v7"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46654"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Plonky3/Plonky3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Plonky3 MultiField32Challenger: transcript malleability and challenge entropy loss"
}

Sightings

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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2026-46654 (GCVE-0-2026-46654)

FKIE_CVE-2026-46654

GHSA-VJ64-RJF3-W3V7

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