Uncontrolled recursion in the ASN.1 parser (Asn1InputStream, Asn1StreamParser) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker to cause a denial of service via a crafted ASN.1 encoding of deeply nested constructed elements (for example SEQUENCE inside SEQUENCE, in definite-length DER or indefinite-length BER form), because each nesting level is parsed by a further recursive call with no bound on depth. About 2,000 levels (8 KB of DER) are enough to exhaust a 1.5 MB thread stack, the .NET main-thread default on Windows, and raise a StackOverflowException, which .NET cannot catch and which terminates the whole process; on threads with larger stacks, parse time instead grows quadratically with depth (about 9 seconds of CPU for a 64 KB input). Any path that parses untrusted ASN.1 is exposed, including X.509 certificates and CRLs, CMS/PKCS#7, PKCS#8/PKCS#12, OCSP and TLS Certificate messages.
Fix
Patch, vendor advisory and mitigation references on NVD 3
- https://github.com/bcgit/bc-csharp/commit/89c81b0da7fe11cd70013285560bbc472cb73901 Patch
- https://github.com/bcgit/bc-csharp/commit/b99f4e3dcea05b57becc79dfa6ad91a54c778d65 Patch
- https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103600 Patch, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 8.7 · bouncycastleNVD modified 2026-10-28 14:48
Affected (CPE criteria) 1
cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:*