# CVE-2017-20240: Crypt::PBKDF2 versions before 0.261630 for Perl are vulnerable to timing attacks

> An attacker can exploit timing discrepancies in key comparison to guess the derived key, compromising password security.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/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:** 12 Jun 2026
- **Updated:** 12 Jun 2026
- **Also known as:** DEBIAN-CVE-2017-20240, GHSA-m538-6wp4-7h22, UBUNTU-CVE-2017-20240

## What is CVE-2017-20240?

CVE-2017-20240 is a medium-severity vulnerability in ARODLAND Crypt::PBKDF2, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Crypt::PBKDF2 versions before 0.261630 for Perl are vulnerable to timing attacks.

These versions use Perl's built-in eq comparison. Discrepancies in timing could be used to guess the underlying derived-key.

Weakness: CWE-208 (Observable Timing Discrepancy)

## Which versions are affected by CVE-2017-20240?


## How do I fix CVE-2017-20240?

Upgrade to a fixed version.

## Is CVE-2017-20240 being exploited?

There is no known exploitation of CVE-2017-20240 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-20240 and fix it if it is affected.

What it is: CVE-2017-20240 is a medium-severity vulnerability in ARODLAND Crypt::PBKDF2, published on 12 Jun 2026. 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-2017-20240 in the wild and no public exploit code.

Affected product: ARODLAND Crypt::PBKDF2. 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-2017-20240/ (Markdown: https://insights.sbomify.com/CVE-2017-20240/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-20240
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-20240
- OSV: https://osv.dev/vulnerability/CVE-2017-20240

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From sbomify Insights: https://insights.sbomify.com/CVE-2017-20240/
Summaries are generated and may contain mistakes; the official description above is the record.