Hi,

The following vulnerability was published for erlang.

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
| libssh2 through 1.11.0; and there could be effects on Bitvise SSH
| through 9.31.


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/erlang/otp/commit/ee67d46285394db95133709cef74b0c462d665aa

Please adjust the affected versions in the BTS as needed.

Regards,
Salvatore

Hi Salvatore,

Reading the latest announcement on the Erlang mailing list I've found
that there is an update of ssh in Erlang 25 which addresses
CVE-2023-48795:
https://erlang.org/pipermail/erlang-announce/2023-December/000260.html

I will try to backport these changes to Erlang currently in stable if
it's necessary. As for the unstable, the newest version will fix this
as well.

Cheers!

Hi Sergei,

Thanks for working on it. I would say, let's start top-down so go
first trough unstable upload, then we can assess the state for it for
the security supported suites (and if it needs a DSA or can go trough
a point release).

There might be e.g. mitigating factor if ChaCha20-Poly1305 and
Encrypt-then-MAC support is missing.

Regards,
Salvatore

We believe that the bug you reported is fixed in the latest version of
erlang, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1059002@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Sergei Golovan <sgolovan@debian.org> (supplier of updated erlang package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Tue, 19 Dec 2023 18:19:42 +0300
Source: erlang
Architecture: source
Version: 1:25.3.2.8+dfsg-1
Distribution: unstable
Urgency: medium
Maintainer: Debian Erlang Packagers <pkg-erlang-devel@lists.alioth.debian.org>
Changed-By: Sergei Golovan <sgolovan@debian.org>
Closes: 1059002
Changes:
 erlang (1:25.3.2.8+dfsg-1) unstable; urgency=medium
 .
   * New upstream release, which fixes CVE-2023-48795 - downgrading security
     features in SSH connections (closes: #1059002).
   * Refresh patches.
   * Bump standards version to 4.6.2.
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We believe that the bug you reported is fixed in the latest version of
erlang, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1059002@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Sergei Golovan <sgolovan@debian.org> (supplier of updated erlang package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Sun, 20 Apr 2025 08:09:59 +0300
Source: erlang
Architecture: source
Version: 1:25.2.3+dfsg-1+deb12u1
Distribution: bookworm-security
Urgency: high
Maintainer: Debian Erlang Packagers <pkg-erlang-devel@lists.alioth.debian.org>
Changed-By: Sergei Golovan <sgolovan@debian.org>
Closes: 1059002 1101713 1103442
Changes:
 erlang (1:25.2.3+dfsg-1+deb12u1) bookworm-security; urgency=high
 .
   [ Salvatore Bonaccorso ]
   * ssh: implement strict KEX (CVE-2023-48795) (Closes: #1059002)
   * ssh: reject SFTP packets exceeding max allowed size (CVE-2025-26618)
   * ssh: fix denial of service due to erroneous processing of large KEX
     init packages (CVE-2025-30211) (Closes: #1101713):
     - reduce log processing for plain connections
     - ignore too long algorithm names
     - limit the length of error messages in reply to invalid packets
     - add the custom_kexinit test to test large KEX init packages processing
   * ssh: fix remote code execution (RCE) by an unauthenticated user
     (CVE-2025-32433) (Closes: #1103442)
 .
   [ Sergei Golovan ]
   * Cleanup the patches.
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