High 8.7Published Oct 2, 2026

CVE-2026-103600Unbounded ASN.1 nesting depth causes process-terminating stack overflow

Updated under an hour ago (2026-10-19 08:30 UTC)

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It affects Legion of the Bouncy Castle Inc. bc-csharp. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.32%, higher than 23% of scored CVEs.

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Every CVE for Legion of the Bouncy Castle Inc. bc-csharp

Exploited in the last 30 days

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.

CVSS: 8.7 HIGH (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness (CWE): CWE-674
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.32% (percentile 23)
Assigned by: bcorg
NVD analysis: Undergoing Analysis
Record last updated: Oct 2, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Legion of the Bouncy Castle Inc. bc-csharp legion_of_the_bouncy_castle:bc_csharp (from the name)	before 2.7.0	CNA record

References

https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103600vendor-advisory
https://github.com/bcgit/bc-csharp/commit/89c81b0da7fe11cd70013285560bbc472cb73901patch
https://github.com/bcgit/bc-csharp/commit/b99f4e3dcea05b57becc79dfa6ad91a54c778d65patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.