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
This vulnerability (CWE-789) exists in the HSS/LMS signature code of bc-csharp before version 2.7.0. When parsing an HSS public key, the level count L is read without validation against the RFC 8554 maximum of 8. Subsequently, signature parsing allocates an array of size L - 1 before reading further signature data. An attacker supplying a crafted public key with an excessive level count can trigger large memory allocations, causing denial of service through memory exhaustion. The flaw allows remote unauthenticated attackers to exploit this by providing both a malicious HSS public key and signature.
Potential Impact
The impact is denial of service caused by memory exhaustion or application crash due to an OutOfMemoryException. A single signature verification can allocate up to about 17 GB of memory, potentially disrupting service availability. There is no indication of code execution or data disclosure from the provided data.
Mitigation Recommendations
A fixed version 2.7.0 of bc-csharp addresses this vulnerability by enforcing the RFC 8554 maximum level count check. Users should upgrade to version 2.7.0 or later to remediate this issue. No other mitigation or temporary fix is indicated. Patch status is confirmed by the vendor advisory specifying affected versions as before 2.7.0.
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
Legion of the Bouncy Castle Inc.
bc-csharp
pkg:nuget/BouncyCastle.CryptographyRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CWE-789) exists in the HSS/LMS signature code of bc-csharp before version 2.7.0. When parsing an HSS public key, the level count L is read without validation against the RFC 8554 maximum of 8. Subsequently, signature parsing allocates an array of size L - 1 before reading further signature data. An attacker supplying a crafted public key with an excessive level count can trigger large memory allocations, causing denial of service through memory exhaustion. The flaw allows remote unauthenticated attackers to exploit this by providing both a malicious HSS public key and signature.
Potential Impact
The impact is denial of service caused by memory exhaustion or application crash due to an OutOfMemoryException. A single signature verification can allocate up to about 17 GB of memory, potentially disrupting service availability. There is no indication of code execution or data disclosure from the provided data.
Mitigation Recommendations
A fixed version 2.7.0 of bc-csharp addresses this vulnerability by enforcing the RFC 8554 maximum level count check. Users should upgrade to version 2.7.0 or later to remediate this issue. No other mitigation or temporary fix is indicated. Patch status is confirmed by the vendor advisory specifying affected versions as before 2.7.0.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- bcorg
- Date Reserved
- 2026-09-30T23:01:10.053Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6abf5de5a43b0b3b8988e876
Added to database: 10/02/2026, 07:31:49 UTC
Last enriched: 10/02/2026, 07:46:58 UTC
Last updated: 10/02/2026, 20:45:56 UTC
Views: 11
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