Date: Thu, 10 Nov 2022 18:22:44 +0000 From: Matthieu Herrb <matthieu@...rb.eu> To: oss-security@...ts.openwall.com Subject: Re: CVE-2022-45063: xterm <375 code execution via font ops On Thu, Nov 10, 2022 at 02:42:41PM +1100, David Leadbeater wrote: > xterm before patch 375 can enable an RCE under certain conditions. > > Fix: > > Upgrade to xterm patch #375 > https://invisible-island.net/xterm/xterm.log.html > > Mitigation: > > Set this Xresource: > XTerm*allowFontOps: false Hi, Running xterm 375 on Arch Linux (Font Ops are enabled by default) and OpenBSD (after re-enabling Font Ops) shows it as still vulnerable using the test below.. > > Details: > > The issue is in the OSC 50 sequence, which is for setting and querying > the font. If a given font does not exist, it is not set, but a query > will return the name that was set. Control characters can't be > included, but the response string can be terminated with ^G. This > essentially gives us a primitive for echoing text back to the terminal > and ending it with ^G. > > It so happens ^G is in Zsh when in vi line editing mode bound to > "list-expand". Which can run commands as part of the expansion leading > to command execution without pressing enter! > > This does mean to exploit this vulnerability the user needs to be > using Zsh in vi line editing mode (usually via $EDITOR having "vi" in > it). While somewhat obscure this is not a totally unknown > configuration. > > In that configuration, something like: > printf "\e]50;i\$(touch /tmp/hack-like-its-1999)\a\e]50;?\a" > cve-2022-45063 > cat cve-2022-45063 # or another way to deliver this to the victim > > Will touch that file. It will leave the line on the user's screen; > I'll leave it as an exercise for the reader to use the vi line editing > commands to hide the evidence. > > Debian, Red Hat and others disable font ops by default (see some > good foresight at or this very list), but users can re-enable them > via a configuration option or menu. Additionally upstream xterm does > not disable them by default, so some distributions include a > vulnerable default configuration. > > This has been assigned CVE-2022-45063. > > David > > > : https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=510030 > : https://www.openwall.com/lists/oss-security/2015/09/20/2 towards the end. -- Matthieu Herrb
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.