CVE-2024-31497VulnerabilityPublished 15 Apr 2024Updated 4 Nov 2025

CVE-2024-31497: putty · n/a

Affects puttySource CVE Database V5

Not known to be exploited · CVSS 5.9 Medium : upgrade to 0.81 when convenient.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 3.1 base score

5.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 5.7% chance of exploitation in 30 days – higher than 92% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.81, 3.67.0, 6.3.3 +1

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Apr 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
GitHubputty/putty`pkg:github/putty/putty`Other threats	Affected <0.81 >=0.68	Fixed in 0.81
GitHubfilezilla-project/filezilla`pkg:github/filezilla-project/filezilla`Other threats	Affected <3.67.0	Fixed in 3.67.0
GitHubwinscp/winscp`pkg:github/winscp/winscp`Other threats	Affected <6.3.3	Fixed in 6.3.3
GitHubtortoisegit/tortoisegit`pkg:github/tortoisegit/tortoisegit`Other threats	Affected <2.15.0.1	Fixed in 2.15.0.1
GitHubtortoisesvn/tortoisesvn`pkg:github/tortoisesvn/tortoisesvn`Other threats	Affected <=1.14.6	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate CVE-2024-31497, European organizations should immediately update all affected software to versions that have patched the biased nonce generation issue: PuTTY 0.81 or later, FileZilla 3.67.0 or later, WinSCP 6.3.3 or later, TortoiseGit 2.15.0.1 or later, and TortoiseSVN versions beyond 1.14.6. Organizations should audit their use of NIST P-521 ECDSA keys, especially those used for SSH authentication and Git commit signing, and consider generating new keys with secure nonce generation. Avoid reusing the same private key across multiple services to limit the impact of a potential compromise. Disable SSH agent forwarding where not strictly necessary, or restrict it to trusted servers only, to reduce exposure to rogue SSH servers. Review and restrict access to signed messages stored in public or semi-public repositories to minimize signature leakage. Implement monitoring for unusual SSH authentication patterns and unauthorized Git commits that could indicate key compromise. Educate developers and system administrators about the risks of key reuse and the importance of timely patching. Finally, consider adopting alternative cryptographic algorithms or key types less susceptible to nonce-related vulnerabilities, such as Ed25519, where feasible.

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.

Impact

For European organizations, the impact of CVE-2024-31497 is considerable due to the widespread use of PuTTY and related clients in enterprise environments for SSH access, file transfers, and Git commit signing. The ability to recover private keys compromises the confidentiality of authentication credentials and code signing keys, enabling attackers to impersonate users and inject malicious code into software supply chains. This can lead to unauthorized access to critical infrastructure, intellectual property theft, and disruption of software development pipelines. Organizations with public or semi-public Git repositories are particularly vulnerable, as attackers may harvest signatures without direct network access. The risk is amplified in environments where private keys are reused across multiple services, increasing the attack surface. Supply-chain attacks facilitated by this vulnerability could have cascading effects on software integrity and trustworthiness across European industries, including finance, manufacturing, and government sectors. Additionally, the involvement of SSH agent forwarding in the attack vector highlights risks in remote work and cloud-based development workflows common in Europe. Although the CVSS score is medium, the potential for key compromise and subsequent unauthorized access elevates the threat's seriousness for organizations relying heavily on these tools.

Summary

CVE-2024-31497 is a cryptographic vulnerability found in PuTTY versions 0.68 through 0.80 prior to 0.81, as well as in related software such as FileZilla, WinSCP, TortoiseGit, and TortoiseSVN. The core issue lies in biased nonce generation during ECDSA signing using the NIST P-521 curve. ECDSA requires a fresh, uniformly random nonce for each signature; bias or reuse of this nonce can leak the private key. In this case, the nonce bias allows an attacker to recover the victim's private key after collecting approximately 60 signatures. The attack scenarios include: (1) an adversary accessing signed messages publicly available in Git repositories where commit signing is used, especially when signatures are generated via Pageant with agent forwarding; (2) a malicious SSH server operator to which the victim connects using the same private key, enabling the attacker to derive the private key from signatures generated during authentication. Once the private key is compromised, the attacker can impersonate the victim, gain unauthorized access to other services using the same key, and potentially conduct supply-chain attacks by injecting malicious code into software repositories. The vulnerability is classified under CWE-338 (Use of Cryptographically Weak Pseudo-Random Number Generator) and has a CVSS v3.1 score of 5.9, indicating medium severity. The attack vector is network-based with high attack complexity, no privileges or user interaction required, and impacts confidentiality but not integrity or availability. The vulnerability affects a broad range of widely used SSH and file transfer clients, making it a significant risk for environments relying on these tools for secure communications and code signing.

CWE-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) (opens in a new tab)
Base weaknessLikelihood of exploit: MediumOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.
Implementation
Use functions or hardware which use a hardware-based random number generation for all crypto. This is the recommended solution. Use CyptGenRandom on Windows, or hw_rand() on Linux.
OWASP Cheat Sheets
Transport Layer Protection (opens in a new tab)
User Privacy Protection (opens in a new tab)
Password Storage (opens in a new tab)
Cryptographic Storage (opens in a new tab)
HSTS (opens in a new tab)
OWASP ASVS 4.0.3
V6.3.3 (opens in a new tab)
V6.3.2 (opens in a new tab)
V6.3.1 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 11 Nov 2025, 18:29 UTC

WeaknessesCWE-338

Technical details

References

Community reviews

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