CVE-2026-4115
PuTTY Ed25519 Signature ecc-ssh.c eddsa_verify signature verification
CVE-2026-4115 is a medium vulnerability (CVSS 6.3) in Putty, published March 22, 2026. Its validity is disputed. EPSS puts the chance of exploitation in the next 30 days at 0.55%, the 46th percentile. Fixed in putty 0.84-1.
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
6.3
PuTTY Ed25519 Signature ecc-ssh.c eddsa_verify signature verification
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.
- Record
CVE-2026-4115- CVSS 4.0
- 6.3 Medium
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 - CVSS 3.1
- 3.7 Low
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 - CVSS 3.0
- 3.7 Low
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 - CVSS 2.0
- 2.6
AV:N/AC:H/Au:N/C:N/I:P/A:N/E:POC/RL:OF/RC:C - Weakness
- CWE-347, CWE-345
- Updated
- 2026-11-02
EUVDEUVD-2026-14301
6.3
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.
- Record
EUVD-2026-14301- CVSS 4.0
- 6.3 Medium
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 - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-p96h-94q2-fh5v
2.9
A vulnerability was detected in PuTTY 0.83. Affected is the function eddsa_verify of the file...
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.
- Record
GHSA-p96h-94q2-fh5v- CVSS 4.0
- 2.9 Low
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 - CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-345
- Updated
- 2026-11-02
NVD
2.9
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.
- Record
CVE-2026-4115- CVSS 4.0
- 2.9 Low
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 - CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N - CVSS 2.0
- 2.6 Low
AV:N/AC:H/Au:N/C:N/I:P/A:N - Weakness
- CWE-345, CWE-347
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-4115
2.9
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.
- Record
DEBIAN-CVE-2026-4115- CVSS 4.0
- 2.9 Low
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 - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-4115
2.9
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.
- Record
UBUNTU-CVE-2026-4115- CVSS 4.0
- 2.9 Low
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 - CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
OSVMGASA-2026-0210 No score
Updated putty packages fix security vulnerabilities
ECDSA signature verification can be made to fail an assertion. Server can provoke a double free in RSA KEX code. Telnet session data is marked with trust sigils after authenticating to a proxy. PuTTY Ed25519 Signature ecc-ssh.c eddsa_verify signature verification. (CVE-2026-4115)
- Record
MGASA-2026-0210- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
puttyDebian:12 |
All versions, plus listed versions 0.78-20.78-2+deb12u10.78-2+deb12u20.78-30.79-1 Show 11 moreShow less0.80-10.81-10.81-20.81-30.82-10.82-20.83-10.83-20.83-30.84-10.85-3 |
None known |
puttyDebian:13 |
All versions, plus listed versions 0.83-30.84-10.85-3 |
None known |
puttyDebian:14 |
before 0.84-1, plus listed versions 0.83-3 |
0.84-1 |
puttyMageia:9 |
before 0.84-1.mga9 | 0.84-1.mga9 |
puttyUbuntu:16.04:LTS |
All versions, plus listed versions 0.65-20.66-10.66-20.66-30.66-4 Show 4 moreShow less0.67-10.67-20.67-3build0.16.04.10.67-3+deb9u1build0.16.04.1 |
None known |
puttyUbuntu:18.04:LTS |
All versions, plus listed versions 0.70-10.70-20.70-30.70-4 |
None known |
puttyUbuntu:20.04:LTS |
All versions, plus listed versions 0.72-10.73-10.73-2 |
None known |
puttyUbuntu:22.04:LTS |
All versions, plus listed versions 0.75-30.76-10.76-2 |
None known |
puttyUbuntu:24.04:LTS |
All versions, plus listed versions 0.78-30.79-10.80-10.80-1build20.80-1build30.81-1 |
None known |
puttyUbuntu:25.10 |
All versions, plus listed versions 0.83-20.83-3 |
None known |
puttyUbuntu:26.10 |
All versions, plus listed versions 0.83-3build10.84-1 |
None known |
puttyUbuntu:26.04:LTS |
All versions, plus listed versions 0.83-30.83-3build1 |
None known |
History
| When | Changed | Sources |
|---|---|---|
| 2026-11-02 | created | CVE List, EUVD, GitHub Advisories, NVD, OSV |
References
vuldb.com?id.352429
vuldb.com?ctiid.352429
vuldb.com?submit.775576
github.com/py-thok/putty-ed25519-malleability-s-plus-l
chiark.greenend.org.uk/~sgtatham/putty/wishlist/eddsa-overlarge-s.html
github.com/py-thok/putty-ed25519-malleability-s-plus-l/blob/main/poc.py
Show 13 moreShow less
git.tartarus.org?p=simon/putty.git;a=commitdiff;h=af996b5ec27ab79bae3882071b9d6acf16044549
rfc-editor.org/rfc/rfc8032
openwall.com/lists/oss-security/2026/05/24/11
nvd.nist.gov/vuln/detail/CVE-2026-4115
github.com/advisories/GHSA-p96h-94q2-fh5v
security-tracker.debian.org/tracker/CVE-2026-4115
advisories.mageia.org/MGASA-2026-0210.html
bugs.mageia.org/show_bug.cgi?id=35585
lists.tartarus.org/pipermail/putty-announce/2026/000042.html
chiark.greenend.org.uk/~sgtatham/putty/wishlist/rsakex-double-free.html
chiark.greenend.org.uk/~sgtatham/putty/wishlist/telnet-trust-sigil.html
ubuntu.com/security/CVE-2026-4115
cve.org/CVERecord?id=CVE-2026-4115