# CVE-2026-52924: sctp: purge outqueue on stale COOKIE-ECHO handling

> A use-after-free in the Linux kernel SCTP implementation allows attackers to cause crashes or potentially execute code via crafted Stale Cookie ERROR messages.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Jun 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-90609, BELL-CVE-2026-52924, DEBIAN-CVE-2026-52924, GHSA-v4hw-q98x-8jmm, ROOT-OS-DEBIAN-11-CVE-2026-52924, ROOT-OS-DEBIAN-12-CVE-2026-52924, ROOT-OS-UBUNTU-2204-CVE-2026-52924, ROOT-OS-UBUNTU-2404-CVE-2026-52924, UBUNTU-CVE-2026-52924

## What is CVE-2026-52924?

CVE-2026-52924 is a critical use after free vulnerability in Linux kernel, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

sctp: purge outqueue on stale COOKIE-ECHO handling

sctp_stream_update() is only invoked when the association is moved into
COOKIE_WAIT during association setup/reconfiguration. In this path, the
outbound stream scheduler state (stream->out_curr) is expected to be
clean, since no user data should have been transmitted yet unless the
state machine has already partially progressed.

However, a corner case exists in sctp_sf_do_5_2_6_stale(): when a
Stale Cookie ERROR is received, the association is rolled back from
COOKIE_ECHOED to COOKIE_WAIT. In this scenario, user data may already
have been queued and even bundled with the COOKIE-ECHO chunk.

During the rollback, sctp_stream_update() frees the old stream table
and installs a new one, but it does not invalidate stream->out_curr.
As a result, out_curr may still point to a freed sctp_stream_out
entry from the previous stream state.

Later, SCTP scheduler dequeue paths (FCFS, RR, PRIO, etc.) rely on
stream->out_curr->ext, which can lead to use-after-free once the old
stream state has been released via sctp_stream_free().

This results in crashes such as (reported by Yuqi):

  BUG: KASAN: slab-use-after-free in sctp_sched_fcfs_dequeue+0x13a/0x140
  Read of size 8 at addr ff1100004d4d3208 by task mini_poc/9312
  CPU: 1 UID: 1001 PID: 9312 Comm: mini_poc Not tainted
     7.1.0-rc1-00305-gbd3a4795d574 #5 PREEMPT(full)
   sctp_sched_fcfs_dequeue+0x13a/0x140
   sctp_outq_flush+0x1603/0x33e0
   sctp_do_sm+0x31c9/0x5d30
   sctp_assoc_bh_rcv+0x392/0x6f0
   sctp_inq_push+0x1db/0x270
   sctp_rcv+0x138d/0x3c10

Fix this by fully purging the association outqueue when handling the
Stale Cookie case. This ensures all pending transmit and retransmit
state is dropped, and any scheduler cached pointers are invalidated,
making it safe to rebuild stream state during COOKIE_WAIT restart.

Updating only stream->out_curr would be insufficient, since queued
and retransmittable data would still reference the old stream state and
trigger later use-after-free in dequeue paths.

Weakness: CWE-825 (Expired Pointer Dereference), CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-52924?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-52924?

Apply the vendor's patch.

## Is CVE-2026-52924 being exploited?

There is no known exploitation of CVE-2026-52924 in the wild and no public exploit code.

Public exploit code:

- https://github.com/Eliot-code/CVE-2026-52924 (github_poc): https://github.com/Eliot-code/CVE-2026-52924

## 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-2026-52924 and fix it if it is affected.

What it is: CVE-2026-52924 is a critical use after free vulnerability in Linux kernel, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-52924 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-2026-52924/ (Markdown: https://insights.sbomify.com/CVE-2026-52924/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52924
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52924
- OSV: https://osv.dev/vulnerability/CVE-2026-52924

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52924/
Summaries are generated and may contain mistakes; the official description above is the record.