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CVE-2024-31497

MEDIUMCVSS 5.9/10EPSS 5.77%

Last modified

CVE-2024-31497 is a medium-severity vulnerability rated 5.9/10 on the CVSS scale. In PuTTY 0.68 through 0.80 before 0.81, biased ECDSA nonce generation allows an attacker to recover a user's NIST P-521 secret key via a quick attack in approximately 60 signatures. This is especially important in a scenario where an adversary is able to read messages signed by PuTTY or Pageant. EPSS estimates a 5.77% chance of exploitation in the next 30 days.

Description

In PuTTY 0.68 through 0.80 before 0.81, biased ECDSA nonce generation allows an attacker to recover a user's NIST P-521 secret key via a quick attack in approximately 60 signatures. This is especially important in a scenario where an adversary is able to read messages signed by PuTTY or Pageant. The required set of signed messages may be publicly readable because they are stored in a public Git service that supports use of SSH for commit signing, and the signatures were made by Pageant through an agent-forwarding mechanism. In other words, an adversary may already have enough signature information to compromise a victim's private key, even if there is no further use of vulnerable PuTTY versions. After a key compromise, an adversary may be able to conduct supply-chain attacks on software maintained in Git. A second, independent scenario is that the adversary is an operator of an SSH server to which the victim authenticates (for remote login or file copy), even though this server is not fully trusted by the victim, and the victim uses the same private key for SSH connections to other services operated by other entities. Here, the rogue server operator (who would otherwise have no way to determine the victim's private key) can derive the victim's private key, and then use it for unauthorized access to those other services. If the other services include Git services, then again it may be possible to conduct supply-chain attacks on software maintained in Git. This also affects, for example, FileZilla before 3.67.0, WinSCP before 6.3.3, TortoiseGit before 2.15.0.1, and TortoiseSVN through 1.14.6.

Metrics

CVSS 3.1
5.9/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS Probability
5.77%

92.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
PuttyPutty>= 0.68, < 0.81
Filezilla-ProjectFilezilla Client< 3.67.0
WinscpWinscp< 6.3.3
TortoisegitTortoisegit< 2.15.0.1
TigrisTortoisesvn< 1.14.6
FedoraprojectFedora38
FedoraprojectFedora39
FedoraprojectFedora40

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2024-31497?
In PuTTY 0.68 through 0.80 before 0.81, biased ECDSA nonce generation allows an attacker to recover a user's NIST P-521 secret key via a quick attack in approximately 60 signatures. This is especially important in a scenario where an adversary is able to read messages signed by PuTTY or Pageant. The required set of signed messages may be publicly readable because they are stored in a public Git service that supports use of SSH for commit signing, and the signatures were made by Pageant through an agent-forwarding mechanism. In other words, an adversary may already have enough signature information to compromise a victim's private key, even if there is no further use of vulnerable PuTTY versions. After a key compromise, an adversary may be able to conduct supply-chain attacks on software maintained in Git. A second, independent scenario is that the adversary is an operator of an SSH server to which the victim authenticates (for remote login or file copy), even though this server is not fully trusted by the victim, and the victim uses the same private key for SSH connections to other services operated by other entities. Here, the rogue server operator (who would otherwise have no way to determine the victim's private key) can derive the victim's private key, and then use it for unauthorized access to those other services. If the other services include Git services, then again it may be possible to conduct supply-chain attacks on software maintained in Git. This also affects, for example, FileZilla before 3.67.0, WinSCP before 6.3.3, TortoiseGit before 2.15.0.1, and TortoiseSVN through 1.14.6.
How severe is CVE-2024-31497?
CVE-2024-31497 has a CVSS score of 5.9/10 (MEDIUM severity). The EPSS model estimates a 5.77% probability of exploitation in the next 30 days.
How do I fix CVE-2024-31497?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST