ML-KEM (Kyber) decapsulation leaks private key information through non-constant-time division in message decoding and ciphertext compression (KyberSlash) (Legion of the Bouncy Castle Inc. BC-JAVA)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.46 % · percentile 40 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- bcorg
- NVD status
- Analyzed
Description
In Bouncy Castle for Java from 1.73 to before 1.78, three ML-KEM (CRYSTALS-Kyber) routines divided secret-derived polynomial coefficients by the modulus q: Poly.toMsg, which decodes the decrypted message, and the ciphertext compression routines Poly.compressPoly and PolyVec.compressPolyVec. An attacker able to measure the timing of a large number of decapsulations performed with the same long-term private key can recover that key. These are the KyberSlash1 (Poly.toMsg) and KyberSlash2 (ciphertext compression) divisions. Compression performed during encapsulation operates on values that become the public ciphertext and is not affected.
Weaknesses (CWE)
- CWE-208 — Observable Timing Discrepancy
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 4.0 | HIGH 8.2 | CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/U:Amber | bcorg |
| CVSS 4.0 | HIGH 8.2 | CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber | NVD · 91579145-5d7b-4cc5-b925-a0262ff19630 (Secondary) |
| CVSS 3.1 | MEDIUM 5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N | NVD · nvd@nist.gov (Primary) |
European references
- ENISA EUVD · EUVD-2024-55702
- GCVE · GCVE-0-2024-14041
CERT-FR advisories
- CERTFR-2026-AVI-1165 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:bouncycastle:bc-java:*:*:*:*:*:*:*:*≥ 1.73 < 1.78
Affected products
| Product | Versions |
|---|---|
| Legion of the Bouncy Castle Inc. · BC-JAVA | affected 1.73 < 1.78 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |