{"schema":"threatline.record/2","record":{"id":"CVE-2026-103603","aliases":[],"summary":"Unbounded HSS public key level count allows huge array allocation during signature verification","details":"Memory allocation with excessive size value in the HSS/LMS signature code (HssPublicKeyParameters, HssSignature) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker who can supply both an HSS public key and a signature to cause a denial of service through memory exhaustion via a public key encoding with an excessive level count, because the level count L read when parsing an HSS public key was not checked against the RFC 8554 maximum of 8, and signature parsing then allocated an array of L - 1 entries before reading any further signature data. A single verification can commit up to about 17 GB of memory or fail with an OutOfMemoryException.","categories":["Unclassified"],"product":"bc-csharp","vendor":"Legion of the Bouncy Castle Inc.","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-103603","source_modified_at":"2026-10-02T17:44:48.251Z","fetched_at":"2026-10-23T18:52:38.922436Z","product":"bc-csharp","vendor":"Legion of the Bouncy Castle Inc.","versions":[{"status":"affected","version":"0","lessThan":"2.7.0","versionType":"semver"}],"defaultStatus":"unaffected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-103603","source_modified_at":"2026-10-02T17:44:48.251Z","fetched_at":"2026-10-23T18:52:38.922436Z","package":{"name":"bc-csharp","ecosystem":null},"version":"2.7.0","basis":"first unaffected version stated in the CVE record"}],"cvss":8.7,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00412,"percentile":0.34378,"score_date":"2026-10-23"},"published_at":"2026-10-02T07:10:34.017Z","modified_at":"2026-10-02T17:44:48.251Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-103603","fetched_at":"2026-10-23T18:52:38.922436Z","source_modified_at":"2026-10-02T17:44:48.251Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-103603","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103603","tags":["vendor-advisory"]},{"source":"CVE List","url":"https://github.com/bcgit/bc-csharp/commit/f47ad47c7b5745b53d3f9ac711a5a419a272a5d7","tags":["patch"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"yes","technical_impact":"partial","assessed_at":"2026-10-02T17:44:39.796207Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-02T17:44:48.251Z","content_hash":"726c7939d2a5bc2716e5514c5a490ae1ac10aaecbdf3295b1d2a2adfa0a18169"}}