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CVE-2026-77991 is a privileged remote code execution vulnerability in Joomla Event Manager versions before 5.0.1. The extension's administrator source model permits writing dangerous file types, including PHP. An authenticated user with high administrative privileges can use this behavior to place attacker-controlled server-side code and execute it in the Joomla environment.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This seven-file repository contains a standalone Python proof of concept, documentation, an AGPLv3 license, and a local Docker Compose lab. The primary entry point, CVE-2026-77991-Abraxas-Labs.py, is a Python HTTP client that authenticates to Joomla's administrator interface, extracts anti-CSRF tokens, accesses com_jem's source editor using a base64-encoded filename, and posts to option=com_jem&task=source.save. It attempts to save an echo-only PHP witness as poc_witness.php below media/com_jem/css, then fetches the file to verify PHP execution. The stated vulnerable condition is insufficient filename/type validation in JEM's source-save path in versions through 5.0.0; version 5.0.1 is described as enforcing a CSS filename policy. Although the script banner contains an unauthenticated-POST claim, both the executable flow and README clearly require administrator authentication, CSRF tokens, and com_jem edit authorization; this is therefore a privileged/authenticated RCE PoC, not an unauthenticated exploit. The lab uses Joomla 5 on PHP 8.3 and MySQL 8.0, with Joomla exposed only at 127.0.0.1:8088.
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6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A privileged remote-code-execution vulnerability in Joomla Event Manager versions earlier than 5.0.1. Its administrator source model permits writing dangerous file types, including PHP, enabling code execution.
A privileged remote-code-execution vulnerability in Joomla Event Manager versions earlier than 5.0.1. An authenticated administrator can use the administrator source model to write dangerous file types, including PHP files, enabling remote code execution.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.