TI-2026-03565 Aliases CVE-2026-4115 GHSA-p96h-94q2-fh5v

PuTTY Ed25519 Signature ecc-ssh.c eddsa_verify signature verification

MEDIUM 61CWE-345Published 2026-03-22 · Updated 2026-05-25

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: High
Attack requirements: None
Impact type: Security bypass
Confidentiality · integrity · availability: None · Low · None
Fix status: No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-345.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00554 46th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by the CNA and NVD

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
—	PuTTY	0.83	—	No fix listed	CNA

PuTTY Vendor— Affected 0.83 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:putty:putty:0.83:::::::*	0.83	Vulnerable	PuTTY

cpe:2.3:a:putty:putty:0.83:*:*:*:*:*:*:* Versions 0.83 Vulnerable ·PuTTY

Remediation

No fixed version listed by the sources yet.

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product

Red Hat

Timeline

2026-10-02 Threatist record created from CVE-2026-4115
2026-10-03 Alias added: GHSA-p96h-94q2-fh5v

References

Exploit 1

https://github.com/py-thok/putty-ed25519-malleability-s-plus-l/blob/main/poc.py

Patch 1

https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=af996b5ec27ab79bae3882071b9d6acf16044549

Advisory 2

Other 1

https://www.rfc-editor.org/rfc/rfc8032#section-8.4

TI-2002-01283 Multiple SSH2 servers and clients do not properly handle large packets or large fields… CVSS 2.0HIGH 10.0
TI-2023-26623 The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6… CVSS 3.1MEDIUM 5.9
TI-2017-04321 The ssh_agent_channel_data function in PuTTY before 0.68 allows remote attackers to have… CVSS 3.0CRITICAL 9.8
TI-2002-01281 Multiple SSH2 servers and clients do not properly handle packets or data elements with… CVSS 2.0HIGH 10.0
TI-2004-00914 Integer signedness error in the ssh2_rdpkt function in PuTTY before 0.56 allows remote… CVSS 2.0HIGH 10.0
TI-2002-01284 Multiple SSH2 servers and clients do not properly handle strings with null characters in… CVSS 2.0HIGH 10.0

See all 35 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences