{"id":"CVE-2026-103600","state":"PUBLISHED","title":"Unbounded ASN.1 nesting depth causes process-terminating stack overflow","description":"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.","publishedAt":"2026-10-02T07:08:51.653Z","updatedAt":"2026-10-02T17:54:00.089Z","severity":{"score":8.7,"label":"High","version":"4.0","vector":"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","source":"bcorg"},"assigner":"bcorg","products":["Legion of the Bouncy Castle Inc. bc-csharp"],"affected":[{"vendor":"Legion of the Bouncy Castle Inc.","product":"bc-csharp","packageName":"BouncyCastle.Cryptography","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"2.7.0","versionType":"semver"}],"collectionURL":"https://www.nuget.org/packages/BouncyCastle.Cryptography","repo":"https://github.com/bcgit/bc-csharp","programFiles":["crypto/src/asn1/Asn1InputStream.cs","crypto/src/asn1/ASN1StreamParser.cs"]}],"references":["https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103600","https://github.com/bcgit/bc-csharp/commit/89c81b0da7fe11cd70013285560bbc472cb73901","https://github.com/bcgit/bc-csharp/commit/b99f4e3dcea05b57becc79dfa6ad91a54c778d65"],"weaknesses":["CWE-674"],"ingestedAt":"2026-10-29T20:10:23.711Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/103xxx/CVE-2026-103600.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-103600","state":"PUBLISHED","datePublished":"2026-10-02T07:08:51.653Z","dateUpdated":"2026-10-02T17:54:00.089Z","assignerShortName":"bcorg","assignerOrgId":"91579145-5d7b-4cc5-b925-a0262ff19630","dateReserved":"2026-09-30T23:01:10.053Z"},"containers":{"cna":{"title":"Unbounded ASN.1 nesting depth causes process-terminating stack overflow","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Legion of the Bouncy Castle Inc.","product":"bc-csharp","packageName":"BouncyCastle.Cryptography","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"2.7.0","versionType":"semver"}],"collectionURL":"https://www.nuget.org/packages/BouncyCastle.Cryptography","repo":"https://github.com/bcgit/bc-csharp","programFiles":["crypto/src/asn1/Asn1InputStream.cs","crypto/src/asn1/ASN1StreamParser.cs"]}],"references":[{"url":"https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103600","tags":["vendor-advisory"]},{"url":"https://github.com/bcgit/bc-csharp/commit/89c81b0da7fe11cd70013285560bbc472cb73901","tags":["patch"]},{"url":"https://github.com/bcgit/bc-csharp/commit/b99f4e3dcea05b57becc79dfa6ad91a54c778d65","tags":["patch"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"HIGH","baseScore":8.7,"vectorString":"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-674","lang":"en","description":"CWE-674 Uncontrolled Recursion","type":"CWE"}]}],"providerMetadata":{"shortName":"bcorg","orgId":"91579145-5d7b-4cc5-b925-a0262ff19630","dateUpdated":"2026-10-02T07:08:51.653Z"},"impacts":[{"descriptions":[{"lang":"en","value":"Denial of Service (process termination by StackOverflowException; quadratic CPU use on large-stack threads)"}]}],"credits":[{"lang":"en","value":"Yt","type":"finder"}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"Claude Opus 5.5"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-02T17:53:50.650326Z","id":"CVE-2026-103600","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-02T17:54:00.089Z"}}]}}}