---
title: "CVE-2026-59989: Phalcon Volt compiler `join` filter compile-time PHP code injection (SSTI leads to RCE)"
url: https://erroneo.us/security/cve/CVE-2026-59989/
description: "CVE-2026-59989 (phalcon/cphalcon (Composer (PHP))): Phalcon is a high-performance, full-stack PHP framework. In 5.15.0 and earlier, resolveFilter in…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-08-21
date_modified: 2026-08-27
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-59989"
kev: false
cvss: 9.2
epss: 0.00543
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.5% , percentile 45: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 45% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes phalcon/cphalcon (Composer (PHP)) <= 5.15.0, fixed in 5.16.0 . Check your lockfile, including transitive dependencies.

## What it is

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.

## Affected packages

- Composer (PHP) `phalcon/cphalcon` <= 5.15.0 → fixed: 5.16.0

## Affected products (CVE record)

- phalcon cphalcon: < 5.16.0

## Severity

- GitHub_M CVSS 4.0: 9.2 `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`
- GitHub CVSS 4.0: 9.2 `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`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.54% probability of exploitation activity in the next 30 days; percentile 45.

## Sources

- [GitHub Advisory GHSA-hrwp-4hh9-c8r8](https://github.com/advisories/GHSA-hrwp-4hh9-c8r8)
- [CVE.org record CVE-2026-59989](https://www.cve.org/CVERecord?id=CVE-2026-59989)
- [NVD entry CVE-2026-59989](https://nvd.nist.gov/vuln/detail/CVE-2026-59989)
- [github.com](https://github.com/phalcon/cphalcon/security/advisories/GHSA-hrwp-4hh9-c8r8)
- [github.com](https://github.com/phalcon/cphalcon/pull/17217)
- [github.com](https://github.com/phalcon/cphalcon/commit/e434061be3b7161930476c1368c868badc71e1bd)
- [github.com](https://github.com/phalcon/cphalcon/releases/tag/v5.16.0)

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Source page: https://erroneo.us/security/cve/CVE-2026-59989/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt