Bug 2544597

Summary: CVE-2026-103680 tnef: Heap buffer overflow in find_free_number() via numbered-backup suffix generation [fedora-all]
Product: [Fedora] Fedora Reporter: Vladimir Vasilev <vvasilev>
Component: tnefAssignee: Artur Frenszek-Iwicki <fedora>
Status: ASSIGNED --- QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: low Docs Contact:
Priority: low    
Version: rawhideCC: dtimms, fedora
Target Milestone: ---Keywords: Security, SecurityTracking
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Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["f66e10a6-ce1f-4a08-b810-68deba420e31"]}
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On:    
Bug Blocks: 2544478    

Description Vladimir Vasilev 2026-10-01 11:37:56 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.

A flaw was found in tnef. find_free_number() allocates a fixed-size buffer sized for a 5-digit numeric backup suffix, but formats the counter with an unbounded sprintf(). When the --number-backups option is enabled and overwrite is disabled, a crafted TNEF stream that forces roughly 100,000 colliding candidate filenames for a single extracted attachment causes the counter to require six digits, writing past the end of the allocated heap buffer. The issue requires a non-default command-line option and a large, specially crafted input to trigger.