CVE-2026-4115 PuTTY Ed25519 Signature ecc-ssh.c eddsa_verify signature verification
Improper Ed25519 signature verification in PuTTY allows remote attackers to bypass authentication checks, though real-world impact is currently doubted.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-4115?
CVE-2026-4115 is a medium-severity vulnerability in PuTTY, published on 22 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A vulnerability was detected in PuTTY 0.83. 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. The attack may be performed from remote. The attack requires a high level of complexity. The exploitability is told to be difficult. The exploit is now public and may be used. The real existence of this vulnerability is still doubted at the moment. The patch is identified as af996b5ec27ab79bae3882071b9d6acf16044549. 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.
Which versions are affected by CVE-2026-4115?
It affects 1 product.
Products include Putty Putty.
How do I fix CVE-2026-4115?
Apply the vendor's patch.
Is CVE-2026-4115 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4115 exists.
Other vulnerabilities in PuTTY
Sources
Also known as DEBIAN-CVE-2026-4115, GHSA-p96h-94q2-fh5v, MGASA-2026-0210, UBUNTU-CVE-2026-4115.