Bug 1779566 (CVE-2019-19331)

Summary: CVE-2019-19331 knot-resolver: DNS packets taking few seconds to process with full CPU utilization leads to DoS
Product: [Other] Security Response Reporter: msiddiqu
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED UPSTREAM QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: jv+fedora, pspacek, security-response-team, tkrizek
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: knot-resolver 4.3.0 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2019-12-06 13:04:53 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: 1780511, 1780513    
Bug Blocks:    
Attachments:
Description Flags
big-rrset.patch
none
cname-limit.patch none

Description msiddiqu 2019-12-04 09:36:34 UTC 
DNS replies with very many resource records might be processed very inefficiently, in extreme cases taking even several CPU seconds for each such uncached message.  For example, a few thousand A records can be squashed into one DNS message (limit is 64kB).

To execute an attack it is enough to:
+ own a rogue authoritative server or utilize an existing name with a huge RRset, and
+ trigger DNS query for that name from the resolver to be attacked

References: 

https://gitlab.labs.nic.cz/knot/knot-resolver/tags/v4.3.0
Comment 1 msiddiqu 2019-12-04 09:56:37 UTC 
From upstream:

Most of the issue can be mitigated by updating libknot dependency to >= 2.9.1. Otherwise a complete fix will be released in Knot Resolver 4.3.0, which also does not require libknot update. The attached patches are applicable to recent releases (when doc diff is stripped).
Comment 2 msiddiqu 2019-12-04 10:00:22 UTC 
Created attachment 1641993 [details]
big-rrset.patch
Comment 3 msiddiqu 2019-12-04 10:00:58 UTC 
Created attachment 1641994 [details]
cname-limit.patch
Comment 4 msiddiqu 2019-12-06 08:28:32 UTC 
Public via: 

https://www.openwall.com/lists/oss-security/2019/12/04/4
https://seclists.org/oss-sec/2019/q4/119

Lifting embargo.
Comment 5 Dhananjay Arunesh 2019-12-06 09:04:18 UTC 
Created knot-resolver tracking bugs for this issue:

Affects: fedora-all [bug 1780511]
Comment 6 Dhananjay Arunesh 2019-12-06 09:04:51 UTC 
Created knot-resolver tracking bugs for this issue:

Affects: epel-7 [bug 1780513]
Comment 7 Product Security DevOps Team 2019-12-06 13:04:53 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.