Debian LTS: DLA-3794-1: putty Security Advisory Updates
Summary
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
