Bug 2558953

Summary:	CVE-2026-69184 c-ares: c-ares: CPU exhaustion denial of service via unbounded DNS name compression pointer chains [fedora-43]
Product:	[Fedora] Fedora	Reporter:	Srikanth Balasubramanian <sbalasub>
Component:	c-ares	Assignee:	Tom "spot" Callaway <spotrh>
Status:	NEW ---	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	high	Docs Contact:
Priority:	high
Version:	43	CC:	spotrh
Target Milestone:	---	Keywords:	Security, SecurityTracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:	{"flaws": ["d93ac6dd-e8d8-4c20-8324-d2a419edf13f"]}
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	2538396

Description Srikanth Balasubramanian 2026-10-22 13:27:04 UTC

Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

c-ares is an asynchronous resolver library. Prior to 1.34.7, ares_dns_name_parse() enforces backward DNS compression pointers but does not bound the total pointer hops or assembled name length. A malicious DNS server can send a response containing a long descending pointer chain and many resource records whose NAME or RDATA fields refer to the chain, causing repeated decompression work that grows quadratically with message size. A single crafted response can stall the single-threaded c-ares event loop and deny DNS resolution, without causing memory corruption or information disclosure. This issue is fixed in version 1.34.7.

Comment 1 Aoife Moloney 2026-11-10 19:59:30 UTC

This message is a reminder that Fedora Linux 43 is nearing its end of life.
Fedora will stop maintaining and issuing updates for Fedora Linux 43 on 2026-12-02.
It is Fedora's policy to close all bug reports from releases that are no longer
maintained. At that time this bug will be closed as EOL if it remains open with a
'version' of '43'.

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