A heap buffer overflow occurs in the DTLS 1.3 ACK serialization path of wolfSSL before a peer is authenticated. The overflow is caused by integer truncation when calculating the length of the ACK record‑number list, which results in an undersized buffer that an attacker can overrun. This memory corruption can lead to arbitrary code execution or denial of service on the target system.

wolfSSL versions 5.9.0 and earlier that enable DTLS 1.3 are affected. All builds using these library versions, regardless of operating system or platform, are at risk.

The CVSS score of 8.8 classifies the vulnerability as high severity, and the EPSS score is not available, though the absence from the CISA KEV list does not reduce the risk. An unauthenticated attacker can remotely send crafted DTLS messages before authentication completes, triggering the overflow and potentially executing code or crashing the host.