Bug 2553137

Summary: CVE-2026-39834 apptainer: golang.org/x/crypto/ssh: Denial of Service due to integer overflow in SSH channel write [epel-all]
Product: [Fedora] Fedora EPEL Reporter: Avinash Hanwate <ahanwate>
Component: apptainerAssignee: Dave Dykstra <dwd>
Status: CLOSED NOTABUG QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: epel10CC: dwd, go-sig
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["2d749e5e-fe0a-4fae-8339-549023987a9d"]}
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Clone Of: Environment:
Last Closed: 2026-10-15 18:16:52 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 2480676    

Description Avinash Hanwate 2026-10-15 09:42:55 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.

When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation.
Comment 1 Dave Dykstra 2026-10-15 18:16:52 UTC 
Apptainer does not use the vulnerable code.