Bug 2017636 (CVE-2021-25219)

Summary: CVE-2021-25219 bind: Lame cache can be abused to severely degrade resolver performance
Product: [Other] Security Response Reporter: Huzaifa S. Sidhpurwala <huzaifas>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: anon.amish, dns-sig, mruprich, pemensik, security-response-team, vonsch, yanmliu, yozone, zdohnal
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: bind 9.11.36, bind 9.16.22, bind 9.17.19 Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in the way bind processes broken responses from authoritative servers. This caching mechanism could be abused by an attacker to significantly degrade resolver performance.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2022-05-12 02:15:15 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: 2017637, 2017638, 2018037    
Bug Blocks: 2017640    

Description Huzaifa S. Sidhpurwala 2021-10-27 04:58:42 UTC 
As per upstream report:

The lame-ttl option controls how long named caches certain types of broken responses from authoritative servers (see the security advisory for details). This caching mechanism could be abused by an attacker to significantly degrade resolver performance. The vulnerability has been mitigated by changing the default value of lame-ttl to 0 and overriding any explicitly set value with 0, effectively disabling this mechanism altogether. ISC's testing has determined that doing that has a negligible impact on resolver performance while also preventing abuse. 

Administrators may observe more traffic towards servers issuing certain types of broken responses than in previous BIND 9 releases.
Comment 3 Doran Moppert 2021-10-28 04:25:36 UTC 
Public via: https://kb.isc.org/v1/docs/cve-2021-25219
Comment 4 Doran Moppert 2021-10-28 04:25:58 UTC 
Created bind tracking bugs for this issue:

Affects: fedora-all [bug 2018037]
Comment 13 errata-xmlrpc 2022-05-10 15:20:26 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2022:2092 https://access.redhat.com/errata/RHSA-2022:2092
Comment 14 Product Security DevOps Team 2022-05-12 02:15:13 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-2021-25219