CVE-2026-103603: CWE-789 Memory Allocation with Excessive Size Value in Legion of the Bouncy Castle Inc. bc-csharp
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.
AI Analysis
Technical Summary
The vulnerability exists in the HSS/LMS signature code of Legion of the Bouncy Castle Inc. bc-csharp library versions prior to 2.7.0. When parsing an HSS public key, the level count L is read but not validated against the RFC 8554 maximum of 8. This unchecked value is then used during signature parsing to allocate an array of size L - 1 before reading further signature data. An attacker supplying a crafted public key with an excessive level count can cause the application to allocate an excessive amount of memory, leading to denial of service via memory exhaustion.
Potential Impact
A remote unauthenticated attacker can cause a denial of service by triggering excessive memory allocation during signature verification. This can result in the application consuming large amounts of memory (up to about 17 GB) or crashing with an OutOfMemoryException, potentially disrupting service availability.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid processing untrusted HSS public keys or signatures. Monitor for updates from Legion of the Bouncy Castle Inc. regarding patches or official mitigations.
CVE-2026-103603: CWE-789 Memory Allocation with Excessive Size Value in Legion of the Bouncy Castle Inc. bc-csharp
Description
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.
CVSS v4.0
Score 8.7high
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability exists in the HSS/LMS signature code of Legion of the Bouncy Castle Inc. bc-csharp library versions prior to 2.7.0. When parsing an HSS public key, the level count L is read but not validated against the RFC 8554 maximum of 8. This unchecked value is then used during signature parsing to allocate an array of size L - 1 before reading further signature data. An attacker supplying a crafted public key with an excessive level count can cause the application to allocate an excessive amount of memory, leading to denial of service via memory exhaustion.
Potential Impact
A remote unauthenticated attacker can cause a denial of service by triggering excessive memory allocation during signature verification. This can result in the application consuming large amounts of memory (up to about 17 GB) or crashing with an OutOfMemoryException, potentially disrupting service availability.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid processing untrusted HSS public keys or signatures. Monitor for updates from Legion of the Bouncy Castle Inc. regarding patches or official mitigations.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-gpr4-c479-xrw4
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-103603"]
- Database Specific Severity
- HIGH
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6abfeeb7a43b0b3b89e560a3
Added to database: 10/02/2026, 17:49:43 UTC
Last enriched: 10/02/2026, 18:21:15 UTC
Last updated: 10/02/2026, 22:45:56 UTC
Views: 5
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