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.
Does this matter?
Lower severity and a low EPSS score (5.77%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 5.9 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- EPSS
- 5.77% probability · 93th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-338
- Affected
- putty/putty · filezilla-project/filezilla client · winscp/winscp · tortoisegit/tortoisegit · tigris/tortoisesvn · fedoraproject/fedora
- Source
- cve@mitre.org
References
- http://www.openwall.com/lists/oss-security/2024/04/15/6Mailing List, Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2275183Issue Tracking
- https://bugzilla.suse.com/show_bug.cgi?id=1222864Issue Tracking
- https://docs.ccv.brown.edu/oscar/connecting-to-oscar/ssh/ssh-agent-forwarding/key-generation-and-agent-forwarding-with-puttyProduct
- https://filezilla-project.org/versions.phpRelease Notes
- https://git.tartarus.org/?h=c193fe9848f50a88a4089aac647fecc31ae96d27&p=simon/putty.gitMailing List, Patch
- https://github.com/advisories/GHSA-6p4c-r453-8743Third Party Advisory
- https://github.com/daedalus/BreakingECDSAwithLLLThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2024/06/msg00014.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IZS3B37GNGWOOV7QU7B7JFK76U4TOP4V/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MMHILY2K7HQGQRHOC375KRRG2M6625RD/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PUOTQVGC4DISVHQGSPUYGXO6TLDK65LA/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WFDZBV7ZCAZ6AH3VCQ34SSY7L3J7VZXZ/Mailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WMJH7M663BVO3SY6MFAW2FAZWLLXAPRQ/Mailing List, Third Party Advisory
- https://news.ycombinator.com/item?id=40044665Issue Tracking
- https://security-tracker.debian.org/tracker/CVE-2024-31497Third Party Advisory
- https://securityonline.info/cve-2024-31497-critical-putty-vulnerability-exposes-private-keys-immediate-action-required/Press/Media Coverage
- https://tartarus.org/~simon/putty-snapshots/htmldoc/Chapter9.html#pageant-forwardProduct
- https://tortoisegit.orgThird Party Advisory
- https://twitter.com/CCBalert/status/1780229237569470549Press/Media Coverage
- https://twitter.com/lambdafu/status/1779969509522133272Press/Media Coverage
- https://winscp.net/eng/news.phpThird Party Advisory
- https://www.bleepingcomputer.com/news/security/putty-ssh-client-flaw-allows-recovery-of-cryptographic-private-keys/Press/Media Coverage
- https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.htmlRelease Notes, Vendor Advisory
- https://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/vuln-p521-bias.htmlVendor Advisory
- https://www.openwall.com/lists/oss-security/2024/04/15/6Mailing List, Third Party Advisory
- https://www.reddit.com/r/sysadmin/comments/1c4wmoj/putty_vulnerability_affecting_v068_to_v08/Press/Media Coverage
- http://www.openwall.com/lists/oss-security/2024/04/15/6Mailing List, Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2275183Issue Tracking
- https://bugzilla.suse.com/show_bug.cgi?id=1222864Issue Tracking
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.