# CVE-2021-42694: Code injection in n/a

> Attackers can inject malicious code via homoglyph identifiers in dependencies, bypassing human review and executing code in downstream applications.

- **Severity:** High 8.3 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 1 Nov 2021
- **Updated:** 29 Oct 2024
- **Also known as:** GHSA-m3pq-m926-j2h4

## What is CVE-2021-42694?

CVE-2021-42694 is a high-severity code injection vulnerability in n/a, published on 1 Nov 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

An issue was discovered in the character definitions of the Unicode Specification through 14.0. The specification allows an adversary to produce source code identifiers such as function names using homoglyphs that render visually identical to a target identifier. Adversaries can leverage this to inject code via adversarial identifier definitions in upstream software dependencies invoked deceptively in downstream software. NOTE: the Unicode Consortium offers the following alternative approach to presenting this concern. An issue is noted in the nature of international text that can affect applications that implement support for The Unicode Standard (all versions). Unless mitigated, an adversary could produce source code identifiers using homoglyph characters that render visually identical to but are distinct from a target identifier. In this way, an adversary could inject adversarial identifier definitions in upstream software that are not detected by human reviewers and are invoked deceptively in downstream software. The Unicode Consortium has documented this class of security vulnerability in its document, Unicode Technical Report #36, Unicode Security Considerations. The Unicode Consortium also provides guidance on mitigations for this class of issues in Unicode Technical Standard #39, Unicode Security Mechanisms.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2021-42694?

It affects 1 product.


Products: Unicode Unicode.

## How do I fix CVE-2021-42694?

No fix has been published for CVE-2021-42694 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-42694 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-42694 exists.

Public exploit code:

- Generate malicious files using recently published homoglyphic-attack (CVE-2021-42694) (github_poc): https://github.com/simplylu/CVE-2021-42694
- https://github.com/k271266/CVE-2021-42694 (github_poc): https://github.com/k271266/CVE-2021-42694

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-42694 and fix it if it is affected.

What it is: CVE-2021-42694 is a high-severity code injection vulnerability in n/a, published on 1 Nov 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-42694 exists.

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-2021-42694/ (Markdown: https://insights.sbomify.com/CVE-2021-42694/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-42694
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-42694
- OSV: https://osv.dev/vulnerability/CVE-2021-42694

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-42694/
Summaries are generated and may contain mistakes; the official description above is the record.