Bug 2494375

Summary: CVE-2026-27145 apptainer: golang crypto/x509: Denial of Service via excessive processing of DNS SAN entries [fedora-all]
Product: [Fedora] Fedora Reporter: jkelly <jkelly>
Component: apptainerAssignee: Dave Dykstra <dwd>
Status: CLOSED ERRATA QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: rawhideCC: dwd, go-sig
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["1765a0c8-adb1-4223-88bf-d35a230e256a"]}
Fixed In Version: apptainer-1.5.2-1.fc44 apptainer-1.5.2-1.fc43 Doc Type: ---
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2026-07-03 00:55:48 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 14:28:36 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 2026-06-30 20:44:57 UTC 
FEDORA-2026-f8ab642466 (apptainer-1.5.2-1.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-f8ab642466
Comment 2 Fedora Update System 2026-06-30 20:45:03 UTC 
FEDORA-2026-ca1825e29e (apptainer-1.5.2-1.fc44) has been submitted as an update to Fedora 44.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-ca1825e29e
Comment 3 Fedora Update System 2026-07-03 00:55:48 UTC 
FEDORA-2026-ca1825e29e (apptainer-1.5.2-1.fc44) has been pushed to the Fedora 44 stable repository.
If problem still persists, please make note of it in this bug report.
Comment 4 Fedora Update System 2026-07-03 01:09:39 UTC 
FEDORA-2026-f8ab642466 (apptainer-1.5.2-1.fc43) has been pushed to the Fedora 43 stable repository.
If problem still persists, please make note of it in this bug report.