# CVE-2021-47026: RDMA/rtrs-clt: destroy sysfs after removing session from active list

> A use-after-free vulnerability in the Linux kernel RDMA client allows attackers to cause denial of service or execute code via race conditions during session removal.

- **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:** 28 Feb 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47026, GHSA-h6m9-gq43-hhq2, UBUNTU-CVE-2021-47026

## What is CVE-2021-47026?

CVE-2021-47026 is a high-severity use after free vulnerability in Linux kernel, published on 28 Feb 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:

RDMA/rtrs-clt: destroy sysfs after removing session from active list

A session can be removed dynamically by sysfs interface "remove_path" that
eventually calls rtrs_clt_remove_path_from_sysfs function.  The current
rtrs_clt_remove_path_from_sysfs first removes the sysfs interfaces and
frees sess->stats object. Second it removes the session from the active
list.

Therefore some functions could access non-connected session and access the
freed sess->stats object even-if they check the session status before
accessing the session.

For instance rtrs_clt_request and get_next_path_min_inflight check the
session status and try to send IO to the session.  The session status
could be changed when they are trying to send IO but they could not catch
the change and update the statistics information in sess->stats object,
and generate use-after-free problem.
(see: "RDMA/rtrs-clt: Check state of the rtrs_clt_sess before reading its
stats")

This patch changes the rtrs_clt_remove_path_from_sysfs to remove the
session from the active session list and then destroy the sysfs
interfaces.

Each function still should check the session status because closing or
error recovery paths can change the status.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-47026?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47026?

Apply the vendor's patch.

## Is CVE-2021-47026 being exploited?

There is no known exploitation of CVE-2021-47026 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-2021-47026 and fix it if it is affected.

What it is: CVE-2021-47026 is a high-severity use after free vulnerability in Linux kernel, published on 28 Feb 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-2021-47026 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-2021-47026/ (Markdown: https://insights.sbomify.com/CVE-2021-47026/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47026
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47026
- OSV: https://osv.dev/vulnerability/CVE-2021-47026

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47026/
Summaries are generated and may contain mistakes; the official description above is the record.