Bug 1623009 – CVE-2018-15853 libxkbcommon: Endless recursion in xkbcomp/expr.c resulting in a crash

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Bug 1623009 - (CVE-2018-15853) CVE-2018-15853 libxkbcommon: Endless recursion in xkbcomp/expr.c resulting in a crash

Summary:	CVE-2018-15853 libxkbcommon: Endless recursion in xkbcomp/expr.c resulting in...

Status:	NEW

Aliases:	CVE-2018-15853

Product:	Security Response
Classification:	Other
Component:	vulnerability (Show other bugs)
Sub Component:
Version:	unspecified
Hardware:	All Linux

Priority	low Severity low
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Assigned To:	Red Hat Product Security
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URL:
Whiteboard:	impact=low,public=20180310,reported=2...
Keywords:	Security

Depends On:	1623038 1642853 1642852
Blocks:	1623044
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Reported:	2018-08-28 07:47 EDT by Andrej Nemec
Modified:	2018-10-25 11:20 EDT (History)
CC List:	3 users (show)

See Also:
Fixed In Version:	libxkbcommon 0.8.1
Doc Type:	If docs needed, set a value
Doc Text:	An uncontrolled recursion flaw was found in libxkbcommon in the way it parses boolean expressions. A specially crafted file provided to xkbcomp could crash the application.
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Description Andrej Nemec 2018-08-28 07:47:07 EDT

Endless recursion exists in xkbcomp/expr.c in xkbcommon and libxkbcommon before 0.8.1, which could be used by local attackers to crash xkbcommon users by supplying a crafted keymap file that triggers boolean negation.

Upstream patch:

https://github.com/xkbcommon/libxkbcommon/commit/1f9d1248c07cda8aaff762429c0dce146de8632a

References:

https://lists.freedesktop.org/archives/wayland-devel/2018-August/039232.html

Comment 2 Riccardo Schirone 2018-10-25 04:34:34 EDT

Created libxkbcommon tracking bugs for this issue:

Affects: fedora-all [bug 1642852]

Comment 3 Riccardo Schirone 2018-10-25 04:36:04 EDT

When parsing a boolean expression that is composed by another boolean expression, like a negated expression, the ExprResolveBoolean() function is recursively called, but on the same expression that was currently analyzed and not on the sub-expression, causing an infinite recursion.

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