# CVE-2023-52582: netfs: Only call folio_start_fscache() one time for each folio

> A local attacker can trigger a kernel crash in the Linux netfs subsystem by exploiting a double-call bug in folio handling during network filesystem operations.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 2 Mar 2024
- **Updated:** 11 May 2026
- **Also known as:** AZL-55796, BELL-CVE-2023-52582, DEBIAN-CVE-2023-52582, GHSA-2g8r-g5wp-xcxp, ROOT-OS-UBUNTU-2204-CVE-2023-52582, UBUNTU-CVE-2023-52582

## What is CVE-2023-52582?

CVE-2023-52582 is a medium-severity vulnerability in Linux kernel, published on 2 Mar 2024. 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:

netfs: Only call folio_start_fscache() one time for each folio

If a network filesystem using netfs implements a clamp_length()
function, it can set subrequest lengths smaller than a page size.

When we loop through the folios in netfs_rreq_unlock_folios() to
set any folios to be written back, we need to make sure we only
call folio_start_fscache() once for each folio.

Otherwise, this simple testcase:

  mount -o fsc,rsize=1024,wsize=1024 127.0.0.1:/export /mnt/nfs
  dd if=/dev/zero of=/mnt/nfs/file.bin bs=4096 count=1
  1+0 records in
  1+0 records out
  4096 bytes (4.1 kB, 4.0 KiB) copied, 0.0126359 s, 324 kB/s
  echo 3 > /proc/sys/vm/drop_caches
  cat /mnt/nfs/file.bin > /dev/null

will trigger an oops similar to the following:

  page dumped because: VM_BUG_ON_FOLIO(folio_test_private_2(folio))
  ------------[ cut here ]------------
  kernel BUG at include/linux/netfs.h:44!
  ...
  CPU: 5 PID: 134 Comm: kworker/u16:5 Kdump: loaded Not tainted 6.4.0-rc5
  ...
  RIP: 0010:netfs_rreq_unlock_folios+0x68e/0x730 [netfs]
  ...
  Call Trace:
    netfs_rreq_assess+0x497/0x660 [netfs]
    netfs_subreq_terminated+0x32b/0x610 [netfs]
    nfs_netfs_read_completion+0x14e/0x1a0 [nfs]
    nfs_read_completion+0x2f9/0x330 [nfs]
    rpc_free_task+0x72/0xa0 [sunrpc]
    rpc_async_release+0x46/0x70 [sunrpc]
    process_one_work+0x3bd/0x710
    worker_thread+0x89/0x610
    kthread+0x181/0x1c0
    ret_from_fork+0x29/0x50

## Which versions are affected by CVE-2023-52582?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2023-52582?

Apply the vendor's patch.

## Is CVE-2023-52582 being exploited?

There is no known exploitation of CVE-2023-52582 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-52582 and fix it if it is affected.

What it is: CVE-2023-52582 is a medium-severity vulnerability in Linux kernel, published on 2 Mar 2024. 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-2023-52582 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2023-52582/ (Markdown: https://insights.sbomify.com/CVE-2023-52582/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-52582
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-52582
- OSV: https://osv.dev/vulnerability/CVE-2023-52582

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-52582/
Summaries are generated and may contain mistakes; the official description above is the record.