PT-2026-26977 · Putty · Putty

Pythok + 1 · Published 2026-01-01 · Updated 2026-05-25 · CVE-2026-4115

Positive Technologies (AI Summary)

CVSS v3.1

3.7

Low

Base vector

AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Name of the Vulnerable Software and Affected Versions PuTTY version 0.83

Description An issue exists in the Ed25519 Signature Handler component within the eddsa verify() function of the crypto/ecc-ssh.c file. This flaw allows for the improper verification of cryptographic signatures, which could be exploited remotely. The attack is characterized by high complexity and is considered difficult to execute.

Recommendations Apply the patch identified as af996b5ec27ab79bae3882071b9d6acf16044549 for version 0.83.

Exploit

Fix

Improper Verification of Cryptographic Signature

Insufficient Verification of Data Authenticity

Weakness Enumeration

CWE-347

CWE-345

Related Identifiers

CVE-2026-4115

Affected Products

Putty

References · 19

• 🔥 https://github.com/py-thok/putty-ed25519-malleability-s-plus-l/blob/main/poc.py · Exploit
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-4115 · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2026-4115 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2026-4115 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2026-4115 · Security Note
• https://ubuntu.com/security/CVE-2026-4115 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-4115 · Security Note
• https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=af996b5ec27ab79bae3882071b9d6acf16044549 · Patch
• https://github.com/py-thok/putty-ed25519-malleability-s-plus-l · Note
• https://vuldb.com/?submit.775576 · Note
• https://vuldb.com/?ctiid.352429 · Note
• https://twitter.com/cyberbivash/status/2035701275120042024 · Twitter Post
• https://rfc-editor.org/rfc/rfc8032#section-8.4 · Note
• https://twitter.com/CVEnew/status/2035992539631686068 · Twitter Post
• https://vuldb.com/?id.352429 · Note