TI-2026-42539 Aliases CVE-2026-59644 GHSA-xrmp-pcg8-5q9v

MLS hash-ratchet honours arbitrary 32-bit generation counter from sender

MEDIUM 44CWE-834Published 2026-08-03 · Updated 2026-08-03

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: —
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA.

Summary

In Bouncy Castle for Java before 1.85, MLS hash-ratchet honours arbitrary 32-bit generation counter from sender.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00493 42nd percentileScored 2026-11-07

Fix Fixed BC-JAVA (Legion of the Bouncy Castle Inc.): 1.85

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Legion of the Bouncy Castle Inc.	BC-JAVA	1.73 to before 1.85	1.85	Patch available	CNA

BC-JAVA VendorLegion of the Bouncy Castle Inc. Affected 1.73 to before 1.85 Fixed in 1.85 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:bouncycastle:bc-java::::::::	before 1.85	Vulnerable	Legion of the Bouncy Castle Inc.

cpe:2.3:a:bouncycastle:bc-java:*:*:*:*:*:*:*:* Versions before 1.85 Vulnerable ·Legion of the Bouncy Castle Inc.

Remediation

Fix · CNA BC-JAVA (Legion of the Bouncy Castle Inc.) Fixed in 1.85

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

Release · 2026-08-03
Legion of the Bouncy Castle BC-JAVA 1.85
32 records Highest priority Priority MEDIUM 23 MEDIUM, 9 LOW
Other records, highest priority first
- TI-2026-42545 MTI/A0 DH agreement exponentiates unvalidated peer valuePriority MEDIUM 48
- TI-2026-42533 JSSE hostname verifier CN-fallback enabled by default despite documented opt-inPriority MEDIUM 48
- TI-2026-41816 Stapled OCSP response accepted without binding to the checked certificatePriority MEDIUM 48
Show all 32 records →

Timeline

2026-10-02 Threatist record created from CVE-2026-59644
2026-10-03 Alias added: GHSA-xrmp-pcg8-5q9v

References

Patch 1

https://github.com/bcgit/bc-java/commit/610d8757d855afe197df0de6d831cb75c81e3b9f

Advisory 1

https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059644

TI-2018-15967 Legion of the Bouncy Castle Legion of the Bouncy Castle Java Cryptography APIs 1.58 up to… CVSS 3.1CRITICAL 9.8
TI-2017-09736 BouncyCastle JCE TLS Bleichenbacher/ROBOT CVSS 3.0HIGH 7.5
TI-2026-42545 MTI/A0 DH agreement exponentiates unvalidated peer value CVSS 4.0CRITICAL 9.3
TI-2026-42533 JSSE hostname verifier CN-fallback enabled by default despite documented opt-in CVSS 4.0CRITICAL 9.3
TI-2026-41816 Stapled OCSP response accepted without binding to the checked certificate CVSS 4.0CRITICAL 9.3
TI-2026-07701 Name Constraints bypass via trailing dot in rfc822Name and URI CVSS 4.0CRITICAL 9.3

See all 52 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences