Widely used Java crypto library; allows certificate validation bypass enabling MITM/identity spoofing across many apps, high-impact and newsworthy.
CVE-2026-8763
Bouncy Castle name-constraints bypass via trailing dot in rfc822Name/URI.
Is CVE-2026-8763 being exploited?
Not confirmed. CVE-2026-8763 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.43% probability of exploitation in the next 30 days.
How severe is CVE-2026-8763?
CVE-2026-8763 is rated Critical with a CVSS score of 9.3. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-8763?
Yes. A fix has been recorded for CVE-2026-8763. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-8763 affect?
CVE-2026-8763 affects Bouncy Castle for Java < 1.85, BC for Java LTS < 2.73.12, BC-FIPS: <1.0.2.7, <2.0.2, <2.1.3. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-8763?
Upgrade to the fixed Bouncy Castle releases immediately and audit cert-using components.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
X.509 name-constraints bypass lets malicious certificates be accepted, enabling MITM, certificate/identity spoofing, and trust-chain abuse.
Immediate action required
- affected>= 1.0.0 and < 1.0.2.7
- affected>= 2.0.0 and < 2.0.2
- affected>= 2.1.0 and < 2.1.3
- affected< 1.85
- affected>= 2.73.0 and < 2.73.12
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.