Bug 1623009 (CVE-2018-15853)

Summary:	CVE-2018-15853 libxkbcommon: xkbcomp: Endless recursion in xkbcomp/expr.c resulting in a crash
Product:	[Other] Security Response	Reporter:	Andrej Nemec <anemec>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	me, peter.hutterer, xgl-maint
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
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 and xkbcomp in the way it parses boolean expressions. A specially crafted file provided to xkbcomp could crash the application.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-08-06 19:19:23 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2418047, 1623038, 1642852, 1642853, 2418046
Bug Blocks:	1623044

Description Andrej Nemec 2018-08-28 11:47:07 UTC

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 08:34:34 UTC

Created libxkbcommon tracking bugs for this issue:

Affects: fedora-all [bug 1642852]

Comment 3 Riccardo Schirone 2018-10-25 08:36:04 UTC

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.

Comment 6 errata-xmlrpc 2019-08-06 12:11:10 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2019:2079 https://access.redhat.com/errata/RHSA-2019:2079

Comment 7 Product Security DevOps Team 2019-08-06 19:19:23 UTC

This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2018-15853