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Debian Security Advisory DSA-5586-1                   security@debian.org
https://www.debian.org/security/                     Salvatore Bonaccorso
December 22, 2023                     https://www.debian.org/security/faq
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Package        : openssh
CVE ID         : CVE-2021-41617 CVE-2023-28531 CVE-2023-48795 CVE-2023-51384
                 CVE-2023-51385
Debian Bug     : 995130 1033166

Several vulnerabilities have been discovered in OpenSSH, an
implementation of the SSH protocol suite.

CVE-2021-41617

    It was discovered that sshd failed to correctly initialise
    supplemental groups when executing an AuthorizedKeysCommand or
    AuthorizedPrincipalsCommand, where a AuthorizedKeysCommandUser or
    AuthorizedPrincipalsCommandUser directive has been set to run the
    command as a different user. Instead these commands would inherit
    the groups that sshd was started with.

CVE-2023-28531

    Luci Stanescu reported that a error prevented constraints being
    communicated to the ssh-agent when adding smartcard keys to the
    agent with per-hop destination constraints, resulting in keys being
    added without constraints.

CVE-2023-48795

    Fabian Baeumer, Marcus Brinkmann and Joerg Schwenk discovered that
    the SSH protocol is prone to a prefix truncation attack, known as
    the "Terrapin attack". This attack allows a MITM attacker to effect
    a limited break of the integrity of the early encrypted SSH
    transport protocol by sending extra messages prior to the
    commencement of encryption, and deleting an equal number of
    consecutive messages immediately after encryption starts.

    Details can be found at https://terrapin-attack.com/

CVE-2023-51384

    It was discovered that when PKCS#11-hosted private keys were
    added while specifying destination constraints, if the PKCS#11
    token returned multiple keys then only the first key had the
    constraints applied.

CVE-2023-51385

    It was discovered that if an invalid user or hostname that contained
    shell metacharacters was passed to ssh, and a ProxyCommand,
    LocalCommand directive or "match exec" predicate referenced the user
    or hostname via expansion tokens, then an attacker who could supply
    arbitrary user/hostnames to ssh could potentially perform command
    injection. The situation could arise in case of git repositories
    with submodules, where the repository could contain a submodule with
    shell characters in its user or hostname.

For the oldstable distribution (bullseye), these problems have been fixed
in version 1:8.4p1-5+deb11u3.

For the stable distribution (bookworm), these problems have been fixed in
version 1:9.2p1-2+deb12u2.

We recommend that you upgrade your openssh packages.

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

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

Mailing list: debian-security-announce@lists.debian.org