CVE-2026-4115
A vulnerability was detected in PuTTY 0.83.
Does this matter?
Lower severity and a low EPSS score (0.53%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 4.0
- 2.9 LOWCVSS:4.0/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/M
- EPSS
- 0.53% probability · 43th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-345, CWE-347
- Affected
- putty/putty
- Source
- cna@vuldb.com
References
- https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=af996b5ec27ab79bae3882071b9d6acf16044549Permissions Required
- https://github.com/py-thok/putty-ed25519-malleability-s-plus-lThird Party Advisory
- https://github.com/py-thok/putty-ed25519-malleability-s-plus-l/blob/main/poc.pyExploit
- https://vuldb.com/?ctiid.352429Permissions Required, VDB Entry
- https://vuldb.com/?id.352429Third Party Advisory, VDB Entry
- https://vuldb.com/?submit.775576Third Party Advisory, VDB Entry
- https://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/eddsa-overlarge-s.htmlThird Party Advisory
- https://www.rfc-editor.org/rfc/rfc8032#section-8.4Technical Description
- http://www.openwall.com/lists/oss-security/2026/05/24/11
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.