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A critical flaw in PuTTY tracked as CVE-2024-31497 allowed recovery of NIST P-521 ECDSA private keys because the client generated biased nonces during signature creation. Public advisories and downstream vendor notices said the issue affected PuTTY-based signing operations and could let attackers derive a private key from a sufficient number of signatures, putting SSH authentication and related trust relationships at risk where vulnerable keys were used.
The vulnerability was disclosed through oss-security and subsequently addressed by multiple Linux vendors, including Red Hat, SUSE, and Debian LTS, while Citrix warned administrators to apply manual mitigations for affected environments. The broad guidance across advisories was to upgrade PuTTY to a fixed release, stop using impacted P-521 keys for signing, and rotate any potentially exposed private keys and dependent authorized keys or certificates to prevent continued compromise.
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5 events from the most recent confirmed update back to the earliest known activity.
Debian issued DLA-3839-1, providing a security update for PuTTY in Debian LTS in response to CVE-2024-31497. This marked an available downstream patch for affected Debian long-term support users.
SUSE published a bug tracker entry for CVE-2024-31497, describing the issue as exposure of NIST P-521 private keys through biased signature generation in PuTTY. The entry marked downstream vendor tracking and assessment of the vulnerability.
Citrix warned administrators about the PuTTY SSH client flaw and advised manual mitigation steps, indicating operational impact for environments relying on PuTTY-based workflows. This represented a vendor response translating the disclosure into deployment guidance.
Follow-on reporting explained that the flaw affects PuTTY clients using NIST P-521 ECDSA keys and warned that attackers could recover private keys from signatures generated by vulnerable versions. Coverage emphasized the severity of the issue and the need for users to rotate affected keys and update software.
A vulnerability affecting PuTTY's ECDSA signature generation was publicly disclosed, showing that biased nonces could allow recovery of NIST P-521 private keys. The issue was assigned CVE-2024-31497 and discussed on oss-security and downstream vendor trackers.
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lists.debian.org
Open sourcebugzilla.suse.com
Open sourcebleepingcomputer.com
Open sourcevicarius.io
Open sourcethehackernews.com
Open sourcebugzilla.redhat.com
Open sourcesecurityonline.info
Open sourceopenwall.com
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A severe flaw in **PuTTY** and several applications that reuse its code can expose private keys used with the NIST P-521 `ECDSA` algorithm. The weakness causes the software to generate insufficiently random nonces, allowing an attacker to recover a victim’s private key after collecting roughly 60 signatures from the vulnerable implementation. The issue affects PuTTY as well as tools including **FileZilla**, **WinSCP**, and **TortoiseGit**; users of **TortoiseSVN** were advised to replace `Plink` with the latest PuTTY version until an official fix becomes available. Organizations were urged to update immediately and treat any affected P-521 key pairs as potentially compromised because recovered keys could be reused for SSH authentication or other trusted public-key access. Separately, a critical compromise in **XZ Utils** introduced malicious code into versions `5.6.0` and `5.6.1`, creating a supply-chain backdoor that could enable unauthorized access on affected Linux systems, with **SSH** identified as a primary exposure path. Defenders were advised to downgrade to version `5.4.6` immediately, consider disabling SSH if rollback was not possible, and verify system integrity because patching alone may not be enough if the backdoor was already exploited. The alerts noted that some Linux distributions had shipped the tainted versions while others were not observed to be vulnerable or had already issued updates.
Jun 29, 2026
A flaw in OpenSSH's GSSAPI key exchange handling was disclosed on the `oss-security` mailing list and later tracked as **CVE-2026-3497**, with Red Hat describing the issue as an information disclosure or denial-of-service condition caused by uninitialized variables. The bug affects OpenSSH deployments that use GSSAPI authentication or key exchange, where improper handling of internal state can allow an attacker to trigger crashes or expose unintended memory contents under certain conditions. Vendor tracking shows the issue moved from public disclosure into downstream remediation, with Red Hat opening Bugzilla case `2447085` for affected products. Separate references to Oracle Linux and a SonicWall advisory indicate vendors were also assessing or mapping related OpenSSH exposure in their own ecosystems, underscoring that the impact extends beyond a single distribution and requires organizations using GSSAPI-enabled SSH services to review patches and product advisories promptly.
Jul 12, 2026
Researchers disclosed the **Terrapin** attack, a man-in-the-middle flaw in the SSH transport protocol tracked as **`CVE-2023-48795`**, that can corrupt the handshake and strip or disable negotiated security features. The attack exploits sequence number manipulation and prefix truncation in the SSH Binary Packet Protocol, affecting connections that use **ChaCha20-Poly1305** and certain **CBC with Encrypt-then-MAC** configurations. The issue impacts OpenSSH before **9.6** and a broad set of SSH clients, servers, libraries, and products; researchers reported that **77%** of Internet-exposed SSH servers supported at least one vulnerable mode and **57%** preferred one. The disclosure also highlighted implementation-specific flaws in **AsyncSSH**—**`CVE-2023-46445`** and **`CVE-2023-46446`**—that could enable more severe outcomes, including redirecting a victim into an attacker-controlled shell account under the right conditions. Ruhr University Bochum researchers released technical details, proof-of-concept code, and a scanner after coordinated vendor fixes, while maintainers shipped updates including **OpenSSH 9.6**, **PuTTY 0.8**, **libssh 0.10.6/0.9.8**, and **AsyncSSH 2.14.1/2.14.2**. Defenders were urged to patch affected software and, where possible, disable vulnerable cipher modes in favor of safer options such as **AES-GCM**.
Jun 29, 2026