dropbear: CVE-2023-48795

Debian Bug report logs - #1059001
dropbear: CVE-2023-48795

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Salvatore Bonaccorso <carnil@debian.org>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: dropbear: CVE-2023-48795

Date: Tue, 19 Dec 2023 09:08:00 +0100

Source: dropbear
Version: 2022.83-3
Severity: important
Tags: security upstream
X-Debbugs-Cc: carnil@debian.org, Debian Security Team <team@security.debian.org>

Hi,

The following vulnerability was published for dropbear.

CVE-2023-48795[0]:
| The SSH transport protocol with certain OpenSSH extensions, found in
| OpenSSH before 9.6 and other products, 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). The bypass occurs in
| chacha20-poly1305@openssh.com and (if CBC is used) the
| -etm@openssh.com MAC algorithms. This also affects Maverick Synergy
| Java SSH API before 3.1.0-SNAPSHOT, Dropbear through 2022.83, Ssh
| before 5.1.1 in Erlang/OTP, PuTTY before 0.80, AsyncSSH before
| 2.14.2, golang.org/x/crypto before 0.17.0, libssh before 0.10.6, and
| libssh4 through 1.11.0; and there could be effects on Bitvise SSH
| through 9.31.

Dropbear commit [1] implements the Strict KEX mode as well. In my
understanding of [2] the issue might be less of a security concern for
Dropbear itself, not reducing the Dropbear security.

If you fix the vulnerability please also make sure to include the
CVE (Common Vulnerabilities & Exposures) id in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2023-48795
    https://www.cve.org/CVERecord?id=CVE-2023-48795
[1] https://github.com/mkj/dropbear/commit/6e43be5c7b99dbee49dc72b6f989f29fdd7e9356
[2] https://github.com/mkj/dropbear/commit/66bc1fcdee594c6cb1139df0ef8a6c9c5fc3fde3

Please adjust the affected versions in the BTS as needed.

Regards,
Salvatore

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