# CVE-2020-26238: Critical vulnerability found in cron-utils

> Attackers can achieve remote code execution by injecting Java EL expressions into untrusted Cron expressions validated via the @Cron annotation.

- **Severity:** High 7.9 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 24 Nov 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-pfj3-56hm-jwq5

## What is CVE-2020-26238?

CVE-2020-26238 is a high-severity code injection vulnerability in jmrozanec cron-utils, published on 24 Nov 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

Cron-utils is a Java library to parse, validate, migrate crons as well as get human readable descriptions for them. In cron-utils before version 9.1.3, a template Injection vulnerability is present. This enables attackers to inject arbitrary Java EL expressions, leading to unauthenticated Remote Code Execution (RCE) vulnerability. Only projects using the @Cron annotation to validate untrusted Cron expressions are affected. This issue was patched in version 9.1.3.

Weakness: CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component)

## Which versions are affected by CVE-2020-26238?

2 open source packages ship an affected version, including com.cronutils:cron-utils. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `com.cronutils:cron-utils` | Maven | All versions | 9.1.3 |
| `com.cronutils:cron-utils` | Maven | All versions | 9.1.3 |

Products: Cron-Utils Project Cron-Utils.

## How do I fix CVE-2020-26238?

Upgrade com.cronutils:cron-utils to 9.1.3 or later.

## Is CVE-2020-26238 being exploited?

There is no known exploitation of CVE-2020-26238 in the wild and no public exploit code.

## Other vulnerabilities in jmrozanec cron-utils

- [CVE-2021-41269](https://insights.sbomify.com/CVE-2021-41269/): Unauthenticated remote code injection in cron-utils (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-26238 and fix it if it is affected.

What it is: CVE-2020-26238 is a high-severity code injection vulnerability in jmrozanec cron-utils, published on 24 Nov 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-2020-26238 in the wild and no public exploit code.

Affected packages and fixed versions:
- com.cronutils:cron-utils (Maven): affected all versions; fixed in 9.1.3
- com.cronutils:cron-utils (Maven): affected all versions; fixed in 9.1.3

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-2020-26238/ (Markdown: https://insights.sbomify.com/CVE-2020-26238/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-26238
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-26238
- OSV: https://osv.dev/vulnerability/CVE-2020-26238

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-26238/
Summaries are generated and may contain mistakes; the official description above is the record.