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CVE-2026-4115

MEDIUM CVSS 4.0: 6.3 EPSS 0.01%
Updated Mar 23, 2026
Parameter Value
CVSS 6.3 (MEDIUM)
Type CWE-345 (Insufficient Verification of Data), CWE-347 (Improper Verification of Cryptographic Signature)
Public PoC Yes

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
None
No data leak
Integrity
Low
Partial data modification
Availability
None
No disruption

CVSS Vector v4.0