Bug 1972881 (CVE-2021-34549)

Summary:	CVE-2021-34549 tor: hashtable-based CPU denial-of-service attack against relays
Product:	[Other] Security Response	Reporter:	Guilherme de Almeida Suckevicz <gsuckevi>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED UPSTREAM	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	casper, lewk, mh, paul.wouters, rh-bugzilla, s
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Fixed In Version:		Doc Type:	If docs needed, set a value
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Last Closed:	2021-06-16 21:04:50 UTC	Type:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Embargoed:
Bug Depends On:	1972882, 1972883
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Description Guilherme de Almeida Suckevicz 2021-06-16 19:41:52 UTC

Resist a hashtable-based CPU denial-of-service attack against relays. Previously we used a naive unkeyed hash function to look up circuits in a circuitmux object. An attacker could exploit this to construct circuits with chosen circuit IDs, to create collisions and make the hash table inefficient. Now we use a SipHash construction here instead. Fixes bug 40391; bugfix on 0.2.4.4-alpha. This issue is also tracked as TROVE-2021-005 and CVE-2021-34549.

References:
https://lists.torproject.org/pipermail/tor-announce/2021-June/000220.html
https://lists.torproject.org/pipermail/tor-announce/2021-June/000221.html

Comment 1 Guilherme de Almeida Suckevicz 2021-06-16 19:42:57 UTC

Created tor tracking bugs for this issue:

Affects: epel-all [bug 1972883]
Affects: fedora-all [bug 1972882]

Comment 2 Product Security DevOps Team 2021-06-16 21:04:50 UTC

This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.