CVE-2026-63566

  1. OpenCVE
  2. Vulnerabilities (CVE)
  3. CVE-2026-63566
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.

7.5 /10

CVSS v3 : HIGH

V3 Legend

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References
Link Resource
https://github.com/bcgit/bc-csharp/commit/212d06474166d5e85be72c2dd4898313aa5dd5f3 Patch
https://github.com/bcgit/bc-csharp/commit/99afef612458f70f28e7824a09719bfc3a169bda Patch
https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63566 Patch Vendor Advisory
Configurations

Configuration 1 (hide)

cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:*
History

27 Oct 2026, 16:25

Type Values Removed Values Added
References () https://github.com/bcgit/bc-csharp/commit/212d06474166d5e85be72c2dd4898313aa5dd5f3 - () https://github.com/bcgit/bc-csharp/commit/212d06474166d5e85be72c2dd4898313aa5dd5f3 - Patch
References () https://github.com/bcgit/bc-csharp/commit/99afef612458f70f28e7824a09719bfc3a169bda - () https://github.com/bcgit/bc-csharp/commit/99afef612458f70f28e7824a09719bfc3a169bda - Patch
References () https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63566 - () https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63566 - Patch, Vendor Advisory
First Time Bouncycastle bc-csharp
Bouncycastle
CVSS v2 : unknown
v3 : unknown 		v2 : unknown
v3 : 7.5
CPE cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:*

02 Oct 2026, 07:16

Type Values Removed Values Added
New CVE
Information

Published : 2026-10-02 07:16

Updated : 2026-10-27 16:25

NVD link : CVE-2026-63566

Mitre link : CVE-2026-63566

CVE.ORG link : CVE-2026-63566

JSON object : View

Products Affected

bouncycastle

  • bc-csharp
CWE
CWE-789

Memory Allocation with Excessive Size Value