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Debian LTS Advisory DLA-3718-1                debian-lts@lists.debian.org
https://www.debian.org/lts/security/                       Guilhem Moulin
January 25, 2024                              https://wiki.debian.org/LTS
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Package        : php-phpseclib
Version        : 2.0.30-2~deb10u2
CVE ID         : CVE-2023-48795

It was discovered that php-phpseclib, a PHP library for
arbitrary-precision integer arithmetic, was vulnerable to the so-called
Terrapin Attack.

The SSH transport protocol with certain OpenSSH extensions, 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).

For Debian 10 buster, this problem has been fixed in version
2.0.30-2~deb10u2.

We recommend that you upgrade your php-phpseclib packages.

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

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