Bouncy Castle is a widely used Java crypto library; this flaw can cause service disruption across many applications and should be broadly communicated.
CVE-2026-13506
ASN.1 parsing bug in Bouncy Castle can bypass nesting-depth guard and cause DoS.
Is CVE-2026-13506 being exploited?
Not confirmed. CVE-2026-13506 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 0.31% probability of exploitation in the next 30 days.
How severe is CVE-2026-13506?
CVE-2026-13506 is rated High with a CVSS score of 8.7. 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-2026-13506?
Yes. A fix has been recorded for CVE-2026-13506. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-13506 affect?
CVE-2026-13506 affects Bouncy Castle for Java < 1.85, Bouncy Castle Java LTS < 2.73.12, BC-FJA (bc-fips) < 1.0.2.7 (1.0.X), < 2.0.2 (2.0.X), < 2.1.3 (2.1.X). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-13506?
Upgrade to Java 1.85, LTS 2.73.12 or bc-fips 1.0.2.7/2.0.2/2.1.3 immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Crafted ASN.1 inputs can reset nesting-depth checks, enabling deep recursion and remote denial-of-service or crash.
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.