Description
wolfSSL's AVX2-optimized ML-KEM implementation (mlkem_cmp_avx2) compares only 1536 of the 1568 ciphertext bytes during the Fujisaki-Okamoto re-encryption check in ML-KEM-1024 decapsulation. Ciphertexts that differ from the expected re-encryption solely in bytes 1536-1567 bypass implicit rejection and are accepted as valid, breaking IND-CCA2 security. An attacker able to submit chosen ciphertexts to a decapsulation oracle that uses a static ML-KEM-1024 key, and to observe whether the genuine shared secret or the implicit-rejection secret was produced, can use this as a plaintext-checking oracle to recover the private key. A proof of concept recovered a full ML-KEM-1024 private key with approximately 98% success using roughly 350 chosen ciphertexts. The flaw is a deterministic logic error and does not rely on timing measurements.
Published: 2026-06-25
Score: 8.3 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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History

Fri, 26 Jun 2026 16:45:00 +0000

Type Values Removed Values Added
Description ML-KEM-1024 x64 AVX2 implicit rejection failure in the Fujisaki-Okamoto transform breaks IND-CCA2 security, allowing decapsulation to deviate from the implicit-rejection behavior required by the standard. The AVX2 constant-time ciphertext comparison used during decapsulation never compared the final 32-byte block of the 1568-byte ML-KEM-1024 ciphertext, so a ciphertext manipulated only in those final bytes would compare as equal and decapsulation returned the real shared secret instead of performing the required implicit rejection. wolfSSL's AVX2-optimized ML-KEM implementation (mlkem_cmp_avx2) compares only 1536 of the 1568 ciphertext bytes during the Fujisaki-Okamoto re-encryption check in ML-KEM-1024 decapsulation. Ciphertexts that differ from the expected re-encryption solely in bytes 1536-1567 bypass implicit rejection and are accepted as valid, breaking IND-CCA2 security. An attacker able to submit chosen ciphertexts to a decapsulation oracle that uses a static ML-KEM-1024 key, and to observe whether the genuine shared secret or the implicit-rejection secret was produced, can use this as a plaintext-checking oracle to recover the private key. A proof of concept recovered a full ML-KEM-1024 private key with approximately 98% success using roughly 350 chosen ciphertexts. The flaw is a deterministic logic error and does not rely on timing measurements.
Title ML-KEM-1024 x64 AVX2 implicit rejection failure breaks IND-CCA2 security ML-KEM-1024 x64 AVX2 incomplete cipher text comparison enables IND-CCA2 break and static private-key recovery
Weaknesses CWE-327 CWE-697
Metrics cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N'}

 cvssV4_0

{'score': 8.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N'}

Fri, 26 Jun 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Fri, 26 Jun 2026 01:30:00 +0000

Type Values Removed Values Added
First Time appeared Wolfssl
Wolfssl wolfssl
Vendors & Products Wolfssl
Wolfssl wolfssl

Thu, 25 Jun 2026 20:15:00 +0000

Type Values Removed Values Added
Description ML-KEM-1024 x64 AVX2 implicit rejection failure in the Fujisaki-Okamoto transform breaks IND-CCA2 security, allowing decapsulation to deviate from the implicit-rejection behavior required by the standard. The AVX2 constant-time ciphertext comparison used during decapsulation never compared the final 32-byte block of the 1568-byte ML-KEM-1024 ciphertext, so a ciphertext manipulated only in those final bytes would compare as equal and decapsulation returned the real shared secret instead of performing the required implicit rejection.
Title ML-KEM-1024 x64 AVX2 implicit rejection failure breaks IND-CCA2 security
Weaknesses CWE-327
References
Metrics cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N'}

Subscriptions

Wolfssl Wolfssl
cve-icon MITRE

Status: PUBLISHED

Assigner: wolfSSL

Published:

Updated: 2026-06-26T16:35:41.759Z

Reserved: 2026-05-29T15:01:16.331Z

Link: CVE-2026-10097

cve-icon Vulnrichment

Updated: 2026-06-26T13:51:42.276Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-06-26T18:00:06Z

Weaknesses