# CVE-2024-13939: Information disclosure in String::Compare::ConstantTime

> Attackers can determine the length of secret strings via timing attacks in the Perl String::Compare::ConstantTime library.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Mar 2025
- **Updated:** 28 Mar 2025
- **Also known as:** DEBIAN-CVE-2024-13939, GHSA-x2v7-w9j6-rqmx, UBUNTU-CVE-2024-13939

## What is CVE-2024-13939?

CVE-2024-13939 is a high-severity vulnerability in FRACTAL String::Compare::ConstantTime, published on 28 Mar 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

String::Compare::ConstantTime for Perl through 0.321 is vulnerable to timing attacks that allow an attacker to guess the length of a secret string.

As stated in the documentation: "If the lengths of the strings are different, because equals returns false right away the size of the secret string may be leaked (but not its contents)."

This is similar to CVE-2020-36829

Weakness: CWE-203 (Observable Discrepancy), CWE-208 (Observable Timing Discrepancy)

## Which versions are affected by CVE-2024-13939?

It affects 1 product.


Products: Fractal String\.

## How do I fix CVE-2024-13939?

Upgrade to a fixed version.

## Is CVE-2024-13939 being exploited?

There is no known exploitation of CVE-2024-13939 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-13939 and fix it if it is affected.

What it is: CVE-2024-13939 is a high-severity vulnerability in FRACTAL String::Compare::ConstantTime, published on 28 Mar 2025. 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-2024-13939 in the wild and no public exploit code.

Affected product: FRACTAL String::Compare::ConstantTime. 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-2024-13939/ (Markdown: https://insights.sbomify.com/CVE-2024-13939/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-13939
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-13939
- OSV: https://osv.dev/vulnerability/CVE-2024-13939

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From sbomify Insights: https://insights.sbomify.com/CVE-2024-13939/
Summaries are generated and may contain mistakes; the official description above is the record.