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Debian LTS DLA-3839-1 Critical: Putty ECDSA Key Compromise Risk

A biased ECDSA nonce generation allowed an attacker to recover a user's NIST P-521 secret key via a quick attack in approximately 60 signatures. In other words, an adversary may already have enough signature information to compromise a victim's . - ------------------------------------------------------------------------- Debian LTS Advisory DLA-3839-1 This email address is being protected from spambots. You need JavaScript enabled to view it. https://www.debian.org/lts/security/ Bastien Roucariès June 20, 2024 https://wiki.debian.org/LTS - ------------------------------------------------------------------------- Package : putty Version : 0.74-1+deb11u1~deb10u2 CVE ID : CVE-2024-31497 A biased ECDSA nonce generation allowed an attacker to recover a user's NIST P-521 secret key via a quick attack in approximately 60 signatures. 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. This allowed an attacker to (for instance) log in to any servers the victim uses that key for. To obtain these signatures, an attacker need only briefly compromise any server the victim uses the key to authenticate to. Therefore, if you have any NIST-P521 ECDSA key, we strongly recommend you to replace it with a freshly new created with a fixed version of putty. Then, to revoke the old public key and remove it from any machine where you use it to login into, so that a signature from the compromised key has no value any more. 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', 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. For Debian 10 buster, this problem has been fixed in version 0.74-1+deb11u1~deb10u2. Werecommend that you upgrade your putty packages. For the detailed security status of putty please refer to its security tracker page at: https://security-tracker.debian.org/tracker/source-package/putty Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: https://wiki.debian.org/LTS . Ubuntu Security Notice USN-1234-1 addresses vulnerabilities in OpenSSH that jeopardize RSA key integrity under specific conditions.. Putty Security, Debian LTS Advisory, ECDSA Attack, NIST P-521 Security. . Severity: Critical. LinuxSecurity.com Team

Jun 20, 2024 •Critical Debian LTS