# CVE-2026-74363: bpf: fix UAF by restoring RCU-delayed inode freeing in bpffs

> A use-after-free in the Linux kernel's bpffs allows attackers to execute arbitrary code or escalate privileges via concurrent path walking and unlinking.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-74363, DEBIAN-CVE-2026-74363, GHSA-99p6-gfcm-83g8, UBUNTU-CVE-2026-74363

## What is CVE-2026-74363?

CVE-2026-74363 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

bpf: fix UAF by restoring RCU-delayed inode freeing in bpffs

commit 4f375ade6aa9 ("bpf: Avoid RCU context warning when unpinning
htab with internal structs") moved inode cleanup from ->free_inode()
into ->destroy_inode() to avoid sleeping in RCU context when calling
bpf_any_put(). However this removed the RCU delay on freeing the
inode itself and the cached symlink body (i_link), both of which
can be accessed by RCU pathwalk (pick_link, may_lookup etc.).

This causes a use-after-free when a concurrent unlinkat() drops the
last inode reference and destroy_inode() frees the inode immediately,
while another task is still walking the path in RCU mode and reads
inode->i_opflags (offset +2) inside current_time() -> is_mgtime().

KASAN reports:
  BUG: KASAN: slab-use-after-free in is_mgtime include/linux/fs.h:2313
  Read of size 2 at addr ffff8880407e4282 (offset +2 = i_opflags)

The rules (per Al Viro):
  ->destroy_inode()  called immediately, can sleep, use for blocking
                     cleanup e.g. bpf_any_put()
  ->free_inode()     called after RCU grace period, use for freeing
                     inode and anything RCU-accessible e.g. i_link

Fix: split the two concerns properly:
  - keep bpf_any_put() in bpf_destroy_inode() since it is blocking
    and needs to run promptly
  - introduce bpf_free_inode() to handle kfree(i_link) and
    free_inode_nonrcu() with proper RCU delay, preventing the UAF

## Which versions are affected by CVE-2026-74363?


## How do I fix CVE-2026-74363?

Apply the vendor's patch.

## Is CVE-2026-74363 being exploited?

There is no known exploitation of CVE-2026-74363 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74363 and fix it if it is affected.

What it is: CVE-2026-74363 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74363 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-74363/ (Markdown: https://insights.sbomify.com/CVE-2026-74363/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74363
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74363
- OSV: https://osv.dev/vulnerability/CVE-2026-74363

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74363/
Summaries are generated and may contain mistakes; the official description above is the record.