# CVE-2018-21232: Denial of service in n/a

> An attacker can cause a denial of service via stack consumption in the re2c lexer generator due to uncontrolled recursion.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 29 Apr 2020
- **Updated:** 5 Aug 2024
- **Also known as:** AZL-7337, DEBIAN-CVE-2018-21232, ECHO-4fc2-67bd-0a7a, GHSA-pgr8-gpgg-9j5m, MGASA-2021-0299, SUSE-SU-2023:3353-1, UBUNTU-CVE-2018-21232

## What is CVE-2018-21232?

CVE-2018-21232 is a medium-severity denial of service vulnerability in n/a, published on 29 Apr 2020. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

re2c before 2.0 has uncontrolled recursion that causes stack consumption in find_fixed_tags.

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2018-21232?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `re2c` | SUSE:Linux Enterprise Module for Basesystem 15 SP4 | All versions | 1.0.3-150000.3.3.1 |
| `re2c` | SUSE:Linux Enterprise Module for Basesystem 15 SP5 | All versions | 1.0.3-150000.3.3.1 |
| `re2c` | SUSE:Manager Proxy 4.2 | All versions | 1.0.3-150000.3.3.1 |
| `re2c` | SUSE:Manager Server 4.2 | All versions | 1.0.3-150000.3.3.1 |
| `re2c` | openSUSE:Leap 15.4 | All versions | 1.0.3-150000.3.3.1 |
| `re2c` | openSUSE:Leap 15.5 | All versions | 1.0.3-150000.3.3.1 |

Products: Re2c Re2c.

## How do I fix CVE-2018-21232?

Upgrade to a fixed version.

## Is CVE-2018-21232 being exploited?

There is no known exploitation of CVE-2018-21232 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2022-23901](https://insights.sbomify.com/CVE-2022-23901/): Denial of service in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-21232 and fix it if it is affected.

What it is: CVE-2018-21232 is a medium-severity denial of service vulnerability in n/a, published on 29 Apr 2020. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2018-21232 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-2018-21232/ (Markdown: https://insights.sbomify.com/CVE-2018-21232/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-21232
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-21232
- OSV: https://osv.dev/vulnerability/CVE-2018-21232

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-21232/
Summaries are generated and may contain mistakes; the official description above is the record.