PuTTY 0.68 through 0.73 has an Observable Discrepancy leading to an information leak in the algorithm negotiation. This allows man-in-the-middle attackers to target initial connection attempts (where no host key for the server has been cached by the client).

The remote Debian 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-3794 advisory.

  - PuTTY before 0.73 might allow remote SSH-1 servers to cause a denial of service by accessing freed memory     locations via an SSH1_MSG_DISCONNECT message. (CVE-2019-17069)

  - PuTTY 0.68 through 0.73 has an Observable Discrepancy leading to an information leak in the algorithm     negotiation. This allows man-in-the-middle attackers to target initial connection attempts (where no host     key for the server has been cached by the client). (CVE-2020-14002)

  - PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive     authentication response. This makes it easier for an attacker-controlled SSH server to present a later     spoofed authentication prompt (that the attacker can use to capture credential data, and use that data for     purposes that are undesired by the client user). (CVE-2021-36367)

  - The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6 and other     products, allows remote attackers to bypass integrity checks such that some packets are omitted (from the     extension negotiation message), and a client and server may consequently end up with a connection for     which some security features have been downgraded or disabled, aka a Terrapin attack. This occurs because     the SSH Binary Packet Protocol (BPP), implemented by these extensions, mishandles the handshake phase and     mishandles use of sequence numbers. For example, there is an effective attack against SSH's use of     ChaCha20-Poly1305 (and CBC with Encrypt-then-MAC). The bypass occurs in chacha20-poly1305@openssh.com and     (if CBC is used) the -etm@openssh.com MAC algorithms. This also affects Maverick Synergy Java SSH API     before 3.1.0-SNAPSHOT, Dropbear through 2022.83, Ssh before 5.1.1 in Erlang/OTP, PuTTY before 0.80,     AsyncSSH before 2.14.2, golang.org/x/crypto before 0.17.0, libssh before 0.10.6, libssh2 through 1.11.0,     Thorn Tech SFTP Gateway before 3.4.6, Tera Term before 5.1, Paramiko before 3.4.0, jsch before 0.2.15,     SFTPGo before 2.5.6, Netgate pfSense Plus through 23.09.1, Netgate pfSense CE through 2.7.2, HPN-SSH     through 18.2.0, ProFTPD before 1.3.8b (and before 1.3.9rc2), ORYX CycloneSSH before 2.3.4, NetSarang     XShell 7 before Build 0144, CrushFTP before 10.6.0, ConnectBot SSH library before 2.2.22, Apache MINA sshd     through 2.11.0, sshj through 0.37.0, TinySSH through 20230101, trilead-ssh2 6401, LANCOM LCOS and     LANconfig, FileZilla before 3.66.4, Nova before 11.8, PKIX-SSH before 14.4, SecureCRT before 9.4.3,     Transmit5 before 5.10.4, Win32-OpenSSH before 9.5.0.0p1-Beta, WinSCP before 6.2.2, Bitvise SSH Server     before 9.32, Bitvise SSH Client before 9.33, KiTTY through 0.76.1.13, the net-ssh gem 7.2.0 for Ruby, the     mscdex ssh2 module before 1.15.0 for Node.js, the thrussh library before 0.35.1 for Rust, and the Russh     crate before 0.40.2 for Rust. (CVE-2023-48795)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Security fix for CVE-2020-14002.

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website.
Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Simon Tatham reports :

[Release 0.74] fixes the following security issues :

- New configuration option to disable PuTTY's default policy of changing its host key algorithm preferences to prefer keys it already knows. (There is a theoretical information leak in this policy.) [CVE-2020-14002]

- In some situations an SSH server could cause PuTTY to access freed mdmory by pretending to accept an SSH key and then refusing the actual signature. It can only happen if you're using an SSH agent.

ID	Name	Product	Family	Severity
193899	Debian dla-3794 : pterm - security update	Nessus	Debian Local Security Checks	high
138244	Fedora 31 : putty (2020-f4dba093f1)	Nessus	Fedora Local Security Checks	medium
138235	Fedora 32 : putty (2020-35442ce9b7)	Nessus	Fedora Local Security Checks	medium
137870	FreeBSD : PuTTY -- Release 0.74 fixes two security vulnerabilities (6190c0cd-b945-11ea-9401-2dcf562daa69)	Nessus	FreeBSD Local Security Checks	medium

Detections

Analytics

CVE-2020-14002

medium

Tenable Plugins

high

medium

medium

medium