Bouncy Castle bc-csharp is a widely used .NET crypto library; unbounded ASN.1 recursion can crash processes parsing certs/CMS/TLS, impacting many enterprise apps and services.
CVE-2026-103600
Unbounded ASN.1 recursion in Bouncy Castle (bc-csharp) allows remote DoS via crafted certificates.
Is CVE-2026-103600 being exploited?
Not confirmed. CVE-2026-103600 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.
How severe is CVE-2026-103600?
CVE-2026-103600 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-2026-103600?
Yes. A fix has been recorded for CVE-2026-103600. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-103600 affect?
CVE-2026-103600 affects Bouncy Castle bc-csharp < 2.7.0, .NET apps parsing ASN.1: X.509, CRL, CMS/PKCS#7, PKCS#8/12, OCSP, TLS cert messages. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-103600?
Upgrade bc-csharp to 2.7.0+; block/validate untrusted ASN.1 and enforce depth/size limits.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote unauthenticated DoS: crafted deeply nested ASN.1 triggers StackOverflowException or excessive CPU, terminating the process or hanging parsing threads.
Immediate action required
- affected< 2.7.0
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.