CVE-2026-4115 | PuTTY 0.83 Ed25519 Signature crypto/ecc-ssh.c eddsa_verify signature verification

A vulnerability was found in PuTTY 0.83. It has been declared as problematic. Affected is the function eddsa_verify of the file crypto/ecc-ssh.c of the component Ed25519 Signature Handler. The manipulation results in improper verification of cryptographic signature.

This vulnerability was named CVE-2026-4115. The attack may be performed from remote. In addition, an exploit is available.

The real existence of this vulnerability is still doubted at the moment.

It is advisable to implement a patch to correct this issue.

The vendor was contacted early, responded in a very professional manner and quickly released a patch for the affected product. However, at the moment there is no proof that this flaw might have any real-world impact.