Improper Verification of Cryptographic Signature in PuTTY by Simon Tatham
CVE-2026-4115

6.3MEDIUM

Key Information:

Vendor

Simon Tatham

Status
Putty
Vendor
CVE Published:
22 March 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-4115?

A significant vulnerability has been identified in PuTTY 0.83, specifically within the eddsa_verify function of the Ed25519 Signature Handler. This flaw leads to improper verification of cryptographic signatures, allowing potential remote manipulation. Although the exploit has a high complexity level, it is now public, raising concerns about the integrity of systems using this version. Simon Tatham, the vendor, promptly addressed this issue by releasing a patch (af996b5ec27ab79bae3882071b9d6acf16044549). It is advisable for users to apply this patch to enhance the security of their applications, as the real-world impact of this vulnerability remains unproven.

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Affected Version(s)

PuTTY 0.83

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-4115 - Proof of Concept

References

https://vuldb.com/?id.352429
vdb-entrytechnical-description
https://vuldb.com/?ctiid.352429
signaturepermissions-required
https://vuldb.com/?submit.775576
third-party-advisory

CVSS V4

Score:
6.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
High
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

pythok (VulDB User)
VulDB
JSON
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