[SECURITY] [DLA 3794-1] putty security update

[roucaries.bastien@gmail.com]

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