{"id":"CVE-2026-103603","title":"Memory allocation with excessive size value in the HSS/LMS signature code (HssPublicKeyParameters, HssSignature) in Legion of the Bouncy Castle Inc","summary":"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 H…","severity":"high","cvss":8.7,"cvssVector":"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","cwe":["CWE-789"],"vendor":"Legion of the Bouncy Castle Inc.","product":"BouncyCastle.Cryptography","affected":["BouncyCastle.Cryptography < 2.7.0"],"published":"2026-10-02","updated":"2026-10-02","sourceUpdated":"2026-10-02T08:17:00.837","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-103603","references":[{"url":"https://github.com/bcgit/bc-csharp/commit/f47ad47c7b5745b53d3f9ac711a5a419a272a5d7","label":"91579145-5d7b-4cc5-b925-a0262ff19630"},{"url":"https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103603","label":"91579145-5d7b-4cc5-b925-a0262ff19630"}],"tags":["nvd","cve.org"],"cvssSource":"cna","ingestedAt":"2026-10-02T08:14:06.226Z","slug":"CVE-2026-103603","body":"## Overview\n\nMemory 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":47.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}