# CVE-2026-99138: tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO)


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** AZL-111260, BELL-CVE-2026-99138, DEBIAN-CVE-2026-99138, GHSA-xjqr-qmx4-h4w3, UBUNTU-CVE-2026-99138

## What is CVE-2026-99138?

CVE-2026-99138 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

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

tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO)

do_tcp_getsockopt() reads icsk->icsk_ca_ops and dereferences the
get_info function pointer without rcu_read_lock(). With BPF struct_ops
congestion control, ca_ops can point to dynamically allocated memory
that is freed concurrently, resulting in a use-after-free when the
kernel dereferences or calls through the stale pointer.

  BUG: KASAN: slab-use-after-free in do_tcp_getsockopt+0x2037/0x23e0
  Read of size 8 at addr ffff888013701258 by task exploit/149
   do_tcp_getsockopt+0x2037/0x23e0 (net/ipv4/tcp.c:4564)
   tcp_getsockopt+0x91/0xf0
   __sys_getsockopt+0xf7/0x170

Fix this by wrapping the ca_ops load and get_info call within
rcu_read_lock()/rcu_read_unlock(), and using READ_ONCE() to load
the icsk_ca_ops pointer.

## Which versions are affected by CVE-2026-99138?


## How do I fix CVE-2026-99138?

Upgrade to a fixed version.

## Is CVE-2026-99138 being exploited?

There is no known exploitation of CVE-2026-99138 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99138 and fix it if it is affected.

What it is: CVE-2026-99138 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99138 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-2026-99138/ (Markdown: https://insights.sbomify.com/CVE-2026-99138/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99138
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99138
- OSV: https://osv.dev/vulnerability/CVE-2026-99138

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99138/
Summaries are generated and may contain mistakes; the official description above is the record.