- 6.3MediumCVSS base score
- 0.57%Exploitation in 30 daysEPSS · top 53% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- YesPublic exploitsa reference or SSVC says so
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.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. A reference of the record is tagged as an exploit. CISA's SSVC rates its exploitation: a proof of concept is public.
Show the exploits1
References tagged exploit1 reference
Timeline
ID reserved
By VulDB
- 9 days later
· 9 days later
Published
- 2 months later
· 2 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| VulDBCNA (assigner) | 4.0 | Medium6.3 | CVSS: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 |
| VulDBCNA (assigner) | 3.1 | Low3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C |
| VulDBCNA (assigner) | 3.0 | Low3.7 | CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C |
| VulDBCNA (assigner) | 2.0 | Low2.6 | AV:N/AC:H/Au:N/C:N/I:P/A:N/E:POC/RL:OF/RC:C |
| NVDNVD · Modified | 4.0 | Low2.9 | CVSS: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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.57% · top 53% of all CVEs (11 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.3.
Affected products
PuTTY
- affected 0.83
References
References9
- VDB-352429 | PuTTY Ed25519 Signature ecc-ssh.c eddsa_verify signature verification (opens in a new tab)vdb-entrytechnical-description
- VDB-352429 | CTI Indicators (IOB, IOC, IOA) (opens in a new tab)signaturepermissions-required
- Submit #775576 | PuTTY Project (Simon Tatham) PuTTY 0.83 Improper Verification of Cryptographic Signature (opens in a new tab)third-party-advisory
- https://github.com/py-thok/putty-ed25519-malleability-s-plus-l (opens in a new tab)related
- https://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/eddsa-overlarge-s.html (opens in a new tab)related
- https://github.com/py-thok/putty-ed25519-malleability-s-plus-l/blob/main/poc.py (opens in a new tab)exploit
- https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=af996b5ec27ab79bae3882071b9d6acf16044549 (opens in a new tab)patch
- https://www.rfc-editor.org/rfc/rfc8032#section-8.4 (opens in a new tab)related
- http://www.openwall.com/lists/oss-security/2026/05/24/11 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-14301 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-4115)Record last updated .