Bug 2494282

Summary:	CVE-2026-27145 opkssh: golang crypto/x509: Denial of Service via excessive processing of DNS SAN entries [fedora-all]
Product:	[Fedora] Fedora	Reporter:	jkelly <jkelly>
Component:	opkssh	Assignee:	Till Hofmann <thofmann>
Status:	CLOSED ERRATA	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	rawhide	CC:	go-sig, thofmann
Target Milestone:	---	Keywords:	Security, SecurityTracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:	{"flaws": ["1765a0c8-adb1-4223-88bf-d35a230e256a"]}
Fixed In Version:	opkssh-0.15.0-2.fc44 opkssh-0.15.0-2.fc43	Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2026-07-09 00:56:06 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:
Bug Blocks:	2484207

Description jkelly 2026-06-29 14:19:12 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.

(*x509.Certificate).VerifyHostname previously called matchHostnames in a loop over all DNS Subject Alternative Name (SAN) entries. This caused strings.Split(host, ".") to execute repeatedly on the same input hostname. With a large DNS SAN list, verification costs scaled quadratically based on the number of SAN entries multiplied by the hostname's label count. Because x509.Verify validates hostnames before building the certificate chain, this overhead occurred even for untrusted certificates.

Comment 1 Fedora Update System 2026-07-02 21:06:51 UTC

FEDORA-2026-387cf555e7 (opkssh-0.15.0-2.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-387cf555e7

Comment 2 Fedora Update System 2026-07-02 21:14:12 UTC

FEDORA-2026-a7570524a7 (opkssh-0.15.0-2.fc44) has been submitted as an update to Fedora 44.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-a7570524a7

Comment 3 Fedora Update System 2026-07-03 01:27:04 UTC

FEDORA-2026-a7570524a7 has been pushed to the Fedora 44 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-a7570524a7`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-a7570524a7

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 4 Fedora Update System 2026-07-03 01:48:05 UTC

FEDORA-2026-387cf555e7 has been pushed to the Fedora 43 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-387cf555e7`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-387cf555e7

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 5 Fedora Update System 2026-07-09 00:56:06 UTC

FEDORA-2026-a7570524a7 (opkssh-0.15.0-2.fc44) has been pushed to the Fedora 44 stable repository.
If problem still persists, please make note of it in this bug report.

Comment 6 Fedora Update System 2026-07-09 01:08:16 UTC

FEDORA-2026-387cf555e7 (opkssh-0.15.0-2.fc43) has been pushed to the Fedora 43 stable repository.
If problem still persists, please make note of it in this bug report.