What’s Vulnerable › Vulnerabilities

CVE-2024-14041: ML-KEM (Kyber) decapsulation leaks private key information through non-constant-time division in message decoding and ciphertext compression (KyberSlash)

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-07-28 · updated 2026-10-02
• Weakness: CWE-208

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.

Affected products

• Legion of the Bouncy Castle Inc. BC-JAVA: from 1.73 before 1.78 — fixed in 1.78

How to fix

Upgrade to a fixed version: Legion of the Bouncy Castle Inc. BC-JAVA 1.78. Check the vendor advisory for mitigations.

References

• https://github.com/bcgit/bc-java/commit/1590247178f2280defa36421475f015175dfbe9e
• https://github.com/bcgit/bc-java/commit/5adb2c5c5b462a332b01a012bea0784b40b904e5
• https://github.com/bcgit/bc-java/wiki/CVE-2024-14041
• https://kyberslash.cr.yp.to/

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