CVE-2026-8763: Name Constraints bypass via trailing dot in rfc822Name and URI

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-03 · updated 2026-09-02
Weakness: CWE-295

Description

In Bouncy Castle for Java before 1.85, Name Constraints bypass via trailing dot in rfc822Name and URI. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bc-fips 1.0.2.7 (1.0.X series), 2.0.2 (2.0.X series) and 2.1.3 (2.1.X series).

Affected products

Legion of the Bouncy Castle Inc. BC-JAVA: before 1.85 — fixed in 1.85
Legion of the Bouncy Castle Inc. Bouncy Castle for Java LTS: through 2.73.11
Bouncycastle Fips Java Api: from 1.0.0 before 1.0.2.7; from 2.0.0 before 2.0.2; from 2.1.0 before 2.1.3 — fixed in 1.0.2.7, 2.0.2, 2.1.3

How to fix

Upgrade to a fixed version: Legion of the Bouncy Castle Inc. BC-JAVA 1.85; Bouncycastle Fips Java Api 1.0.2.7, 2.0.2, 2.1.3. Check the vendor advisory for mitigations.

References

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