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CVE-2026-4115

PuTTY Ed25519 Signature ecc-ssh.c eddsa_verify signature verification

6.3 MediumFix availableDisputed

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

0.55%Up 0.5 points since Mar 23, 2026
90%50%10%1%

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 MediumCVSS: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 LowCVSS: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 LowCVSS: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 MediumCVSS: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 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/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 LowCVSS: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 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/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 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
CVSS 2.0
2.6 LowAV: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 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/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 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
CVSS 3.1
3.7 LowCVSS: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

Affected packages
PackageAffectedFixed
putty
Debian:12
All versions, plus listed versions
0.78-20.78-2+deb12u10.78-2+deb12u20.78-30.79-1
Show 11 moreShow less
0.80-10.81-10.81-20.81-30.82-10.82-20.83-10.83-20.83-30.84-10.85-3
None known
putty
Debian:13
All versions, plus listed versions
0.83-30.84-10.85-3
None known
putty
Debian:14
before 0.84-1, plus listed versions
0.83-3
0.84-1
putty
Mageia:9
before 0.84-1.mga9
0.84-1.mga9
putty
Ubuntu:16.04:LTS
All versions, plus listed versions
0.65-20.66-10.66-20.66-30.66-4
Show 4 moreShow less
0.67-10.67-20.67-3build0.16.04.10.67-3+deb9u1build0.16.04.1
None known
putty
Ubuntu:18.04:LTS
All versions, plus listed versions
0.70-10.70-20.70-30.70-4
None known
putty
Ubuntu:20.04:LTS
All versions, plus listed versions
0.72-10.73-10.73-2
None known
putty
Ubuntu:22.04:LTS
All versions, plus listed versions
0.75-30.76-10.76-2
None known
putty
Ubuntu:24.04:LTS
All versions, plus listed versions
0.78-30.79-10.80-10.80-1build20.80-1build30.81-1
None known
putty
Ubuntu:25.10
All versions, plus listed versions
0.83-20.83-3
None known
putty
Ubuntu:26.10
All versions, plus listed versions
0.83-3build10.84-1
None known
putty
Ubuntu:26.04:LTS
All versions, plus listed versions
0.83-30.83-3build1
None known

History

History
WhenChangedSources
2026-11-02createdCVE List, EUVD, GitHub Advisories, NVD, OSV

References

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