A single crafted SSH message can trigger an out‑of‑bounds stack write of attacker‑controlled data in any application that uses swift‑nio‑ssh. The vulnerability allows an unauthenticated network attacker to overwrite arbitrary memory locations, which can lead to arbitrary code execution or other severe compromises. The flaw is a classic memory safety issue, matching the typical stack corruption pattern described in the CWE‑122 family.

Apple’s swift‑nio‑ssh library – any application built with a version prior to 0.14.1 is vulnerable. This includes any service that exposes SSH functionality through swift‑nio‑ssh.

The CVE marks the attack as unauthenticated and network‑based, suggesting that an attacker only needs to send a malicious SSH packet. While the EPSS score is < 1% and it is not listed in the CISA KEV catalog, no public exploitation has been reported, so the current known risk is moderate but potentially high if exploited. The CVSS score of 9.8 indicates critical severity.