oss-security - CVE-2022-46663: less -R filtering bypass

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Message-ID: <CAP9KPhB7PqqFt=Of8+6CKiaV=+p=WwYOjG3QF3TEBDDop1125g@mail.gmail.com>
Date: Tue, 7 Feb 2023 10:49:47 -0800
From: David Leadbeater <dgl@....cx>
To: oss-security@...ts.openwall.com
Subject: CVE-2022-46663: less -R filtering bypass

Hi,

I discovered a way to bypass the escape sequence filtering performed
by less -R due to incorrect terminal state machine handling.

The fix is:
https://github.com/gwsw/less/commit/a78e1351113cef564d790a730d657a321624d79c
but not yet part of any less release.

An example that results in a DoS in xterm or iTerm 2 is:
printf "\e]8;;\e0m\e[>0q" > less-example-xtversion
less -R less-example-xtversion

This has the result of getting the terminal to reply with something
like "\eP>|name version". The "P" there makes less scroll up, the ">"
makes it scroll down, and then it prints the same thing to the tty,
rinse, repeat.

This affects GNU less >= 566 (and <609, but version 608 is the last
public release, the later version numbers are snapshots).

David

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