CVE-2026-63566: 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 DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated DTLS peer to cause a denial of service through memory exhaustion via crafted handshake message fragments, because the reassembly buffer for each incoming handshake message was allocated at the 24-bit length declared in the fragment header, without the check against the peer's maximum handshake message size that TLS already applied. A fragment carrying no payload can force an allocation of almost 16 MB, for each of up to 16 pending messages per handshake, before the handshake is authenticated. DTLS servers and DTLS clients are both affected; TLS is not.
AI Analysis
Technical Summary
This vulnerability arises from improper handling of the reassembly buffer size in the DTLS handshake process within bc-csharp versions before 2.7.0. The reassembly buffer is allocated based on a 24-bit length declared in the fragment header without validating against the peer's maximum handshake message size, which TLS enforces. An attacker can send crafted handshake message fragments, including fragments with no payload, to force large memory allocations (up to nearly 16 MB per fragment) for up to 16 pending messages per handshake before authentication. This can lead to denial of service through memory exhaustion on both DTLS clients and servers.
Potential Impact
A remote unauthenticated attacker can cause a denial of service by exhausting memory resources on affected DTLS clients or servers. This can disrupt service availability. TLS implementations are not affected by this issue.
Mitigation Recommendations
A fix is available in bc-csharp version 2.7.0 and later. Users should upgrade to version 2.7.0 or above to remediate this vulnerability. No vendor advisory content was provided to indicate alternative mitigations or temporary fixes. Patch status is confirmed by the affectedVersions field indicating versions before 2.7.0 are vulnerable.
CVE-2026-63566: 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 DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated DTLS peer to cause a denial of service through memory exhaustion via crafted handshake message fragments, because the reassembly buffer for each incoming handshake message was allocated at the 24-bit length declared in the fragment header, without the check against the peer's maximum handshake message size that TLS already applied. A fragment carrying no payload can force an allocation of almost 16 MB, for each of up to 16 pending messages per handshake, before the handshake is authenticated. DTLS servers and DTLS clients are both affected; TLS is not.
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 arises from improper handling of the reassembly buffer size in the DTLS handshake process within bc-csharp versions before 2.7.0. The reassembly buffer is allocated based on a 24-bit length declared in the fragment header without validating against the peer's maximum handshake message size, which TLS enforces. An attacker can send crafted handshake message fragments, including fragments with no payload, to force large memory allocations (up to nearly 16 MB per fragment) for up to 16 pending messages per handshake before authentication. This can lead to denial of service through memory exhaustion on both DTLS clients and servers.
Potential Impact
A remote unauthenticated attacker can cause a denial of service by exhausting memory resources on affected DTLS clients or servers. This can disrupt service availability. TLS implementations are not affected by this issue.
Mitigation Recommendations
A fix is available in bc-csharp version 2.7.0 and later. Users should upgrade to version 2.7.0 or above to remediate this vulnerability. No vendor advisory content was provided to indicate alternative mitigations or temporary fixes. Patch status is confirmed by the affectedVersions field indicating versions before 2.7.0 are vulnerable.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- bcorg
- Date Reserved
- 2026-07-16T23:48:46.075Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6abfc5e2a43b0b3b89c8de27
Added to database: 10/02/2026, 14:55:30 UTC
Last enriched: 10/02/2026, 14:57:00 UTC
Last updated: 10/03/2026, 04:45:56 UTC
Views: 11
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