Bug 2400735 (CVE-2023-53506)

Summary: CVE-2023-53506 kernel: udf: Do not bother merging very long extents
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was discovered in the UDF (Universal Disk Format) filesystem implementation in the Linux Kernel. The merging logic for very long extents attempted to push as much length as possible into the first extent, which introduced a bug. That bug may cause corruption of file extents on the filesystem when certain long-extent merges occur. A local user (with at least low privileges) on a system using the UDF filesystem could trigger this condition by manipulating extent lengths, potentially leading to file corruption (affecting confidentiality, integrity and availability).
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Description OSIDB Bzimport 2025-10-01 12:04:22 UTC 
In the Linux kernel, the following vulnerability has been resolved:

udf: Do not bother merging very long extents

When merging very long extents we try to push as much length as possible
to the first extent. However this is unnecessarily complicated and not
really worth the trouble. Furthermore there was a bug in the logic
resulting in corrupting extents in the file as syzbot reproducer shows.
So just don't bother with the merging of extents that are too long
together.
Comment 1 Jon Moroney 2025-10-01 21:55:43 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025100128-CVE-2023-53506-2778@gregkh/T