CVE-2024-14041

ML-KEM (Kyber) decapsulation leaks private key information through non-constant-time division in message decoding and ciphertext compression (KyberSlash)

State: Published
Severity: 8.2 High
Published: Jul 28, 2026
Updated: Aug 9, 2026
Reserved: Jul 28, 2026

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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.

Scores

CVSS	Score	Vector	Source
4.0	8.2 High	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

Weaknesses

CWE-208 Observable Timing Discrepancy

Affected Products

Product	Versions
BC-JAVALegion of the Bouncy Castle Inc.	1.73 to before 1.78Affected

References

https://github.com/bcgit/bc-java/wiki/CVE-2024-14041vendor-advisory
https://github.com/bcgit/bc-java/commit/5adb2c5c5b462a332b01a012bea0784b40b904e5patch
https://github.com/bcgit/bc-java/commit/1590247178f2280defa36421475f015175dfbe9epatch
https://kyberslash.cr.yp.to/technical-description

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