CVE-2024-31497: PuTTY vulnerability vuln-p521-bias

[XIII]

Every version of the PuTTY tools from 0.68 to 0.80 inclusive has a critical vulnerability in the code that generates signatures from ECDSA private keys which use the NIST P521 curve. (PuTTY, or Pageant, generates a signature from a key when using it to authenticate you to an SSH server.)

Therefore, if you have a key of this type, we recommend you revoke it immediately: remove the old public key from all OpenSSH authorized_keys files, and the equivalent in other SSH servers, so that a signature from the compromised key has no value any more. Then generate a new key pair to replace it.

The good news: the only affected key type is 521-bit ECDSA. That is, a key that appears in Windows PuTTYgen with ecdsa-sha2-nistp521 at the start of the 'Key fingerprint' box, or is described as 'NIST p521' when loaded into Windows Pageant, or has an id starting ecdsa-sha2-nistp521 in the SSH protocol or the key file. Other sizes of ECDSA, and other key algorithms, are unaffected. In particular, Ed25519 is not affected.

PuTTY vulnerability vuln-p521-bias

www.chiark.greenend.org.uk

 

[John Fitzgerald]

New Release, v0.81:

Download PuTTY: latest release (0.81)

www.chiark.greenend.org.uk

 

[sfx2000]

It's not just putty, but code that includes putty... the one that many use here is WinSCP, so make sure you update it as well when updating your putty instance...

=======

- PuTTY 0.68 - 0.80

The following (not necessarily complete) list of products bundle an
affected PuTTY version and are therefore vulnerable as well:

- FileZilla 3.24.1 - 3.66.5
- WinSCP 5.9.5 - 6.3.2
- TortoiseGit 2.4.0.2 - 2.15.0
- TortoiseSVN 1.10.0 - 1.14.6

 

[PR3MIUM]

Source: https://securityaffairs.com/161921/security/putty-ssh-client-flaw.html

The flaw has been fixed in PuTTY 0.81, FileZilla 3.67.0, WinSCP 6.3.3, and TortoiseGit 2.15.0.1. TortoiseSVN users are recommended to configure TortoiseSVN to use Plink from the latest PuTTY 0.81 release when accessing a SVN repository via SSH until a patch becomes available.

Any product or component using ECDSA NIST-P521 keys impacted by the flaw CVE-2024-31497 should be deemed compromised. These keys should be revoked by removing them from authorized_keys, GitHub repositories, and any other relevant platforms.