mkj/dropbear DROPBEAR_2026.90

Dropbear 2026.90

on GitHub

Download tarballs from
https://matt.ucc.asn.au/dropbear/releases/dropbear-2026.90.tar.bz2 or
https://dropbear.nl/mirror/releases/dropbear-2026.90.tar.bz2
The tarball is reproducible from git with release.sh

• Security: server: Fix ability to bypass an authorized_keys "forced_command"
  option by an authenticated user, if Dropbear is running with "-t" option.
  ("-t" is require both password and public key).
  c60db64
  Reported by Jeremy Brown

• Security: server: Open authorized_keys non-blocking. This avoids getting stuck
  with special files, could allow denial of service from local users.
  8b57957
  Reported by Turistu

• Security: scp: Add missed patch to fix CVE-2019-6111 allowing a malicious server
  to overwrite unexpected files.
  143291b
  Patch from OpenSSH, reported missing by Asim Viladi Oglu Manizada @manizada

  Note breaking change: "-r" is now disallowed when the target directory exists
  (an additional change in Dropbear's version). If that's required an alternative
  such as rsync could be used.
  61bd0e3

• Security: scp: Clear setuid/setgid bits on received files.
  443ccc1
  Patch from OpenSSH, tracked as CVE-2026-35385

• Security: client/server: Fix close() of a file descriptor from an out-of-bounds
  read. This seems dificult to exploit but may have unforseen effects.
  067fd38
  Reported by Ankit Singh and @j499261162

• server: Add unix stream forwarding listener support (-R from the client)
  Patch from Brian Dentino @bdentino

• server: Add -M argument for maximum session duration.
  Github PR #409 from Martin Schiller

• server: Add permitlisten authorized_keys option
  This allows limiting to a specific port.
  Github PR #384 from Mitar

• rsa: keys generated with dropbearkey 0.32 or earlier are no longer supported,
  0.33 was released in 2003. RSA exponent blinding is implemented to reduce a
  cache timing side channel. Side channel reported by Ciaran Mullan.

• server: Limit the number of public key queries to 15.
  This is a mitigation against internet-wide scanning of hosts for public keys.
  It doesn't provide much mitigation against targeted enumeration on a
  server, in that case public keys should not be treated as private.
  Reported by HD Moore, details are in the SSHamble presentation.

• server: Disallow client-sent signals when there is a forced command.
  Some programs could have unexpected handling.
  Reported by HD Moore in SSHamble presentation.

• client: Don't attempt PTY requests for non-TTYs.
  Github issue #385

• server: Don't allow client-sent signals when Dropbear is built with
  DROPBEAR_SVR_DROP_PRIVS = 0

• server: Fix closing TCP remote listeners. This has never worked properly.
  Github PR #414

• server: Improve protocol correctness sending replies to tcpip forward
  requests (-L from the client)

• Fix some timeouts being delayed. Github PR #318

• Improve manpage documentation for forced commands

• Fix distclean of config.h and libtom*/Makefile

• Add curve25519 checks required by rfc8032. These have no effect on SSH protocol
  security.

• Fix "ssh-connection" check, reported by Turistu in Github #397.
  Has no effect on program function.