Vulnerability · Published Aug 3, 2026 · Assigned by bcorg
CVE-2026-59644MLS hash-ratchet honours arbitrary 32-bit generation counter from sender
High 8.7
In plain English
A high-severity security flaw in BC-JAVA from Legion of the Bouncy Castle Inc.. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 4.0)8.7High
Exploit odds (30 days)0.5%top 57.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
In Bouncy Castle for Java before 1.85, MLS hash-ratchet honours arbitrary 32-bit generation counter from sender.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | bouncycastle | no fix listed | DEBIAN-CVE-2026-59644 |
| Debian:13 | bouncycastle | no fix listed | DEBIAN-CVE-2026-59644 |
| Debian:14 | bouncycastle | 1.86-1 | DEBIAN-CVE-2026-59644 |
| Ubuntu:26.04:LTS | bouncycastle | no fix listed | UBUNTU-CVE-2026-59644 |
| Ubuntu:26.10 | bouncycastle | no fix listed | UBUNTU-CVE-2026-59644 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Legion of the Bouncy Castle Inc. | BC-JAVA | 1.73 – before 1.85 |
Weakness: CWE-834 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/U:Amber