The vulnerability lies in the RSA and DSA public key parsers of golang.org/x/crypto/ssh, which lack size restrictions on key parameters. A malicious public key containing an exceedingly large modulus or DSA parameter can trigger several minutes of intense CPU usage during signature verification. This results in a denial‑of‑service condition for the SSH service without requiring any prior authentication.

This flaw affects the golang.org/x/crypto/ssh library. Versions released before the fix do not enforce maximum key lengths for RSA and DSA, while recent releases enforce a maximum RSA modulus of 8192 bits and validate DSA parameters in accordance with FIPS 186‑2.

The CVSS score of 7.5 indicates high severity, while the EPSS score is less than 1%, suggesting low probability of exploitation. The vulnerability is not listed in CISA KEV. It can be triggered by unauthenticated clients during public‑key authentication, allowing an attacker to craft a key with large parameters to consume compute resources and degrade service availability.