# CVE-2019-6293: Denial of service in n/a

> Remote attackers can cause a denial of service in the Flex lexical analyzer library via stack exhaustion triggered by specific input patterns.

- **Severity:** Medium 5.5 (`CVSS:3.0/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:** 15 Jan 2019
- **Updated:** 16 Sep 2024
- **Also known as:** AZL-40794, AZL-6424, DEBIAN-CVE-2019-6293, GHSA-grpp-mcmx-p7pc, JLSEC-2026-1293, UBUNTU-CVE-2019-6293

## What is CVE-2019-6293?

CVE-2019-6293 is a medium-severity denial of service vulnerability in n/a, published on 15 Jan 2019. 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

An issue was discovered in the function mark_beginning_as_normal in nfa.c in flex 2.6.4. There is a stack exhaustion problem caused by the mark_beginning_as_normal function making recursive calls to itself in certain scenarios involving lots of '*' characters. Remote attackers could leverage this vulnerability to cause a denial-of-service.

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2019-6293?

It affects 1 product.


Products: Westes Flex.

## How do I fix CVE-2019-6293?

Upgrade to a fixed version.

## Is CVE-2019-6293 being exploited?

There is no known exploitation of CVE-2019-6293 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2006-0459](https://insights.sbomify.com/CVE-2006-0459/): Memory corruption in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-6293 and fix it if it is affected.

What it is: CVE-2019-6293 is a medium-severity denial of service vulnerability in n/a, published on 15 Jan 2019. 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-2019-6293 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-2019-6293/ (Markdown: https://insights.sbomify.com/CVE-2019-6293/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-6293
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-6293
- OSV: https://osv.dev/vulnerability/CVE-2019-6293

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-6293/
Summaries are generated and may contain mistakes; the official description above is the record.