Bug 1827562 (CVE-2019-12521) - CVE-2019-12521 squid: Off-by-one error in addStackElement allows for heap buffer overflow and crash
Summary: CVE-2019-12521 squid: Off-by-one error in addStackElement allows for heap buf...
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2019-12521
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1828373 1828378
Blocks: 1827553
TreeView+ depends on / blocked
 
Reported: 2020-04-24 08:16 UTC by Marian Rehak
Modified: 2021-03-26 18:48 UTC (History)
5 users (show)

Fixed In Version: squid 4.11, squid 5.0.2
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in squid. When Squid is parsing ESI, it keeps the ESI elements in ESIContext. ESIContext contains a buffer for holding a stack of ESIElements. When a new ESIElement is parsed, it is added via addStackElement. addStackElement has a check for the number of elements in this buffer, but it's off by 1, leading to a Heap Overflow of 1 element. The overflow is within the same structure so it can't affect adjacent memory blocks, and thus just leads to a crash while processing.
Clone Of:
Environment:
Last Closed: 2020-11-04 02:25:04 UTC
Embargoed:

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System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2020:4743 0 None None None 2020-11-04 03:32:03 UTC

Description Marian Rehak 2020-04-24 08:16:19 UTC 
When Squid is parsing ESI, it keeps the ESI elements in ESIContext. ESIContext contains a buffer for holding a stack of ESIElements. When a new ESIElement is parsed, it is added via addStackElement. addStackElement has a check for the number of elements in this buffer, but it's off by 1, leading to a Heap Overflow of 1 element. The overflow is within the same structure so it can't affect adjacent memory blocks, and thus just leads to a crash while processing.
Comment 1 Marian Rehak 2020-04-24 08:16:40 UTC 
Upstream Issue:

https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12521.txt
Comment 3 Stefan Cornelius 2020-04-24 11:54:09 UTC 
Patch:
http://www.squid-cache.org/Versions/v4/changesets/squid-4-fdd4123629320aa1ee4c3481bb392437c90d188d.patch
Comment 4 Stefan Cornelius 2020-04-24 11:54:12 UTC 
External References:

http://www.squid-cache.org/Advisories/SQUID-2019_12.txt
Comment 6 Product Security DevOps Team 2020-11-04 02:25:04 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-2019-12521
Comment 7 errata-xmlrpc 2020-11-04 03:32:01 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2020:4743 https://access.redhat.com/errata/RHSA-2020:4743
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