CVE-2026-4115
PuTTY Ed25519 Signature ecc-ssh.c eddsa_verify signature verification
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.
INFO
Published Date :
March 22, 2026, 1:16 p.m.
Last Modified :
April 30, 2026, 6:33 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 2.0 | LOW | [email protected] | ||||
| CVSS 3.1 | LOW | [email protected] | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Apply the vendor-provided patch for PuTTY.
- Update PuTTY to the latest secure version.
- Verify the integrity of the cryptographic implementation.
- Recompile affected components with the patch.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-4115.
| URL | Resource |
|---|---|
| https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=af996b5ec27ab79bae3882071b9d6acf16044549 | Permissions Required |
| https://github.com/py-thok/putty-ed25519-malleability-s-plus-l | Third Party Advisory |
| https://github.com/py-thok/putty-ed25519-malleability-s-plus-l/blob/main/poc.py | Exploit |
| https://vuldb.com/?ctiid.352429 | Permissions Required VDB Entry |
| https://vuldb.com/?id.352429 | Third Party Advisory VDB Entry |
| https://vuldb.com/?submit.775576 | Third Party Advisory VDB Entry |
| https://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/eddsa-overlarge-s.html | Third Party Advisory |
| https://www.rfc-editor.org/rfc/rfc8032#section-8.4 | Technical Description |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-4115 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-4115
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-4115 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-4115 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Apr. 30, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:putty:putty:0.83:*:*:*:*:*:*:* Added Reference Type VulDB: https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=af996b5ec27ab79bae3882071b9d6acf16044549 Types: Permissions Required Added Reference Type VulDB: https://github.com/py-thok/putty-ed25519-malleability-s-plus-l Types: Third Party Advisory Added Reference Type VulDB: https://github.com/py-thok/putty-ed25519-malleability-s-plus-l/blob/main/poc.py Types: Exploit Added Reference Type VulDB: https://vuldb.com/?ctiid.352429 Types: Permissions Required, VDB Entry Added Reference Type VulDB: https://vuldb.com/?id.352429 Types: Third Party Advisory, VDB Entry Added Reference Type VulDB: https://vuldb.com/?submit.775576 Types: Third Party Advisory, VDB Entry Added Reference Type VulDB: https://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/eddsa-overlarge-s.html Types: Third Party Advisory Added Reference Type VulDB: https://www.rfc-editor.org/rfc/rfc8032#section-8.4 Types: Technical Description -
Data Remediation by [email protected]
Apr. 29, 2026
Action Type Old Value New Value Changed CVSS V4.0 Score 6.3 2.9 -
New CVE Received by [email protected]
Mar. 22, 2026
Action Type Old Value New Value Added Tag disputed Added 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. Added CVSS V4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N Added CVSS V2 (AV:N/AC:H/Au:N/C:N/I:P/A:N) Added CWE CWE-345 Added CWE CWE-347 Added Reference https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=af996b5ec27ab79bae3882071b9d6acf16044549 Added Reference https://github.com/py-thok/putty-ed25519-malleability-s-plus-l Added Reference https://github.com/py-thok/putty-ed25519-malleability-s-plus-l/blob/main/poc.py Added Reference https://vuldb.com/?ctiid.352429 Added Reference https://vuldb.com/?id.352429 Added Reference https://vuldb.com/?submit.775576 Added Reference https://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/eddsa-overlarge-s.html Added Reference https://www.rfc-editor.org/rfc/rfc8032#section-8.4