Bug 1646389 (CVE-2018-18020)

Summary:	CVE-2018-18020 qpdf: recursive calls can lead to a DoS in libqpdf/QPDFWriter.cc
Product:	[Other] Security Response	Reporter:	Laura Pardo <lpardo>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED WONTFIX	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	jpopelka, twaugh, zdohnal
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2018-11-28 11:09:42 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:	1646390, 1646391, 1646392
Bug Blocks:	1646395

Description Laura Pardo 2018-11-05 14:02:01 UTC

A flaw was found in QPDF 8.2.1, in libqpdf/QPDFWriter.cc, QPDFWriter::unparseObject and QPDFWriter::unparseChild have recursive calls for a long time, which allows remote attackers to cause a denial of service via a crafted PDF file.


References:
https://github.com/qpdf/qpdf/issues/243

Comment 1 Laura Pardo 2018-11-05 14:02:51 UTC

Created qpdf tracking bugs for this issue:

Affects: epel-6 [bug 1646390]
Affects: fedora-all [bug 1646391]

Comment 3 Stefan Cornelius 2018-11-28 11:09:42 UTC

I failed to reproduce this behavior during my testing. However, the real problem here seems to be the use of an arbitrary limit. Finding such limits is always a balancing act.

If you run into this problem in a real world scenario, please comment and we'll investigate and possibly adjust the limit.