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mageiaGentoo FoundationMGASA-2024-0140
HistoryApr 20, 2024 - 9:11 p.m.

Updated putty & filezilla packages fix security vulnerability

2024-04-2021:11:17
Gentoo Foundation
advisories.mageia.org
24
putty
filezilla
security vulnerability
ecdsa nonce bias
unix

5.9 Medium

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

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

7.2 High

AI Score

Confidence

Low

0.002 Low

EPSS

Percentile

53.6%

The PuTTY client and all related components generate heavily biased ECDSA nonces in the case of NIST P-521. To be more precise, the first 9 bits of each ECDSA nonce are zero. This allows for full secret key recovery in roughly 60 signatures by using state-of-the-art techniques. These signatures can either be harvested by a malicious server (man-in-the-middle attacks are not possible given that clients do not transmit their signature in the clear) or from any other source, e.g. signed git commits through forwarded agents. The nonce generation for other curves is slightly biased as well. However, the bias is negligible and far from enough to perform lattice-based key recovery attacks (not considering cryptanalytical advancements).

5.9 Medium

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

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

7.2 High

AI Score

Confidence

Low

0.002 Low

EPSS

Percentile

53.6%