CVE-2026-103603 (GCVE-0-2026-103603)
Vulnerability from cvelistv5 – Published: 2026-10-02 07:10 – Updated: 2026-10-02 17:44
VLAI
EPSS
VEX
Title
Unbounded HSS public key level count allows huge array allocation during signature verification
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 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.
Severity
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-02 17:44 UTC
CWE
- CWE-789 - Memory Allocation with Excessive Size Value
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103603 | vendor-advisory |
| https://github.com/bcgit/bc-csharp/commit/f47ad47… | patch |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Legion of the Bouncy Castle Inc. | bc-csharp |
Affected:
0 , < 2.7.0
(semver)
|
guessed |
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