# CVE-2021-26955: Memory corruption in n/a

> A soundness violation in the Rust xcb crate allows attackers to trigger memory corruption or crashes by sending unvalidated bytes from an X server.

- **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:** 9 Feb 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-26955, UBUNTU-CVE-2021-26955

## What is CVE-2021-26955?

CVE-2021-26955 is a critical memory corruption vulnerability in n/a, published on 9 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because xcb::xproto::GetAtomNameReply::name() calls std::str::from_utf8_unchecked() on unvalidated bytes from an X server.

Weakness: CWE-252 (Unchecked Return Value)

## Which versions are affected by CVE-2021-26955?

It affects 1 product.


Products: Xcb Project Xcb.

## How do I fix CVE-2021-26955?

Apply the vendor's patch.

## Is CVE-2021-26955 being exploited?

There is no known exploitation of CVE-2021-26955 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-26956](https://insights.sbomify.com/CVE-2021-26956/): Memory corruption in n/a (critical 9.8)
- [CVE-2021-26957](https://insights.sbomify.com/CVE-2021-26957/): Memory corruption in n/a (critical 9.8)
- [CVE-2021-26958](https://insights.sbomify.com/CVE-2021-26958/): Memory corruption in n/a (high 8.8)
- [CVE-2020-36205](https://insights.sbomify.com/CVE-2020-36205/): Memory handling issues in xcb (medium 5.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-26955 and fix it if it is affected.

What it is: CVE-2021-26955 is a critical memory corruption vulnerability in n/a, published on 9 Feb 2021. 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-2021-26955 in the wild and no public exploit code.

Affected product: n/a. 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-2021-26955/ (Markdown: https://insights.sbomify.com/CVE-2021-26955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-26955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26955
- OSV: https://osv.dev/vulnerability/CVE-2021-26955

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-26955/
Summaries are generated and may contain mistakes; the official description above is the record.