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 Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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)

Note that Nessus relies on the presence of the package as reported by the vendor.

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

    - -------------------------------------------------------------------------     Debian LTS Advisory DLA-3794-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                   Bastien Roucaris     April 25, 2024                                https://wiki.debian.org/LTS
    - -------------------------------------------------------------------------

    Package        : putty     Version        : 0.74-1+deb11u1~deb10u1     CVE ID         : CVE-2019-17069 CVE-2020-14002 CVE-2021-36367 CVE-2023-48795     Debian Bug     : 990901

    Putty, a Telnet/SSH client for X, was vulnerable.

    CVE-2019-17069

      PuTTY allowed remote SSH-1 servers to cause a denial       of service by accessing freed memory locations via an       SSH1_MSG_DISCONNECT message.

    CVE-2020-14002

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

    CVE-2021-36367

      PuTTY proceeded with establishing an SSH session even       if it has never sent a substantive authentication response.
      This made 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-2023-48795

       PuTTY was vulnerable to Terrapin attack.  The SSH transport        protocol with certain OpenSSH extensions, allowed 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. 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 and (if CBC is used)        the -etm MAC algorithms.

    For Debian 10 buster, this problem has been fixed in version     0.74-1+deb11u1~deb10u1.

    We recommend that you upgrade your putty packages.

    For the detailed security status of putty please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/putty

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS

Tenable has extracted the preceding description block directly from the Debian security advisory.

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

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - 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)

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
250851	Linux Distros Unpatched Vulnerability : CVE-2020-14002	Nessus	Misc.	medium
193899	Debian dla-3794 : pterm - security update	Nessus	Debian Local Security Checks	critical
406596	Alpine: multiple putty packages: security update to 0.74-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	medium
406596	Alpine: multiple putty packages: security update to 0.74-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	medium
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

medium

critical

medium

medium

medium

medium

medium