PatchTheCVECVE-2026-63566: Memory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReass
CVE-2026-63566 is a high-severity flaw (CVSS 7.5) affecting bc-csharp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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, w
Why this priority
- High severity
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.4% (top 69%) |
| CISA exploited list | No |
| Weakness | CWE-789 |
| Published | 2026-10-02 |
| Last modified | 2026-10-27 |
Last updated 2026-10-27 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-63566?
bc-csharp: upgrade to 2.7.0. Exact commands for each OS are on this page.
Is CVE-2026-63566 being exploited?
CVE-2026-63566 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-63566 affect?
CVE-2026-63566 affects bc-csharp. Severity is high (CVSS 7.5). 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
How urgent is CVE-2026-63566?
Priority 39/100. High severity; Remotely exploitable, no login, no user action
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