# CVE-2026-89830: f2fs: fix valid block count leak on data block allocation failure

CVE-2026-89830 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-89830, released September 23, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-89830
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 16, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-89830

## Description

In the Linux kernel, the following vulnerability has been resolved:  f2fs: fix valid block count leak on data block allocation failure  In __allocate_data_block(), when allocating a new data block (dn->data_blkaddr == NULL_ADDR), inc_valid_block_count() is called first to increment total_valid_block_count and i_blocks. If the subsequent f2fs_allocate_data_block() fails, the function returns the error directly without rolling back the already-incremented block counts, causing a permanent leak.  Fix this by calling dec_valid_block_count() to undo the increment before returning the error. The condition old_blkaddr == NULL_ADDR precisely identifies the case where inc_valid_block_count() was called.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.111-1 | [DEBIAN-CVE-2026-89830](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89830.md) | Sep 23, 2026 |
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-89830](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89830.md) | Sep 23, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.111-1~deb12u1 | [DEBIAN-CVE-2026-89830](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89830.md) | Sep 23, 2026 |

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Data as of 2026-11-09T13:31:49Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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