GHSA-vj3m-2g9h-vm4p

Multiple RCE vectors were found in Grav CMS. Three are critical, two are high.

1. Unsafe unserialize() in JobQueue — direct RCE gadget (Critical)

system/src/Grav/Common/Scheduler/JobQueue.php:465 calls unserialize(base64_decode(...)) without restricting allowed_classes. The Job class has calluserfunc_array($this->command, $this->args) in its execution path, which is a direct gadget chain — inject a serialized Job with command = 'system' and args = ['whoami'].

The same codebase actually has a Serializable trait that correctly restricts classes, so this inconsistency stands out.

2. Unsafe unserialize() in FileCache — arbitrary class instantiation (Critical)

system/src/Grav/Framework/Cache/Adapter/FileCache.php:75 does unserialize($value, ['allowed_classes' => true]). That true allows instantiation of any class. If an attacker can write to the cache directory (via any file write primitive), they get object injection → RCE.

3. Unsafe unserialize() in Session (High)

system/src/Grav/Common/Session.php:116 — same allowed_classes => true pattern on session data. Lower severity since session storage is typically more restricted.

4. Command injection in git clone (Critical)

system/src/Grav/Console/Cli/InstallCommand.php:150 — only $this->destination uses escapeshellarg(). The $data['branch'], $data['url'], and $data['path'] variables go directly into the shell command without escaping. Admin-accessible via plugin/theme installation.

5. SSTI blocklist bypass (High)

system/src/Grav/Common/Security.php:267-286 — cleanDangerousTwig() blocks twigarraymap and twigarrayfilter but not twigarrayreduce. Also missing filegetcontents and fwrite from the dangerous function blocklist. An attacker who can inject Twig templates can bypass the security filter.

All five are independently exploitable. The unserialize issues are the most concerning since they don't require admin access if there's any file write primitive.

— ProScan AppSec | proscan.one

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Maintainer note — fix applied (2026-04-24)

Fixed in Grav core on the 2.0 branch: commit c66dfeb5f (items #1, #2, #3, #4) and commit 38685ac25 + c66dfeb5f (item #5) — ships in 2.0.0-beta.2.

All five vectors addressed:

1. Scheduler\JobQueue unsafe unserialize — serialized_job now carries a sibling serializedjobhmac signed with Security::getNonceKey(). reconstructJob refuses to unserialize an item whose HMAC is missing/mismatched and falls through to the safe structured-fields rebuild. A tampered queue file can no longer smuggle a forged Job for direct RCE via Job::exec → calluserfunc_array.  

   → system/src/Grav/Common/Scheduler/JobQueue.php

1. FileCache unsafe unserialize — same HMAC-integrity approach; see separate GHSA-gwfr-jfjf-92vv.  

   → system/src/Grav/Framework/Cache/Adapter/FileCache.php

1. Session::getFlashObject unsafe unserialize — payload now wrapped in a v2|<hmac>|<serialized> envelope; legacy/forged envelopes return null instead of triggering unserialize.  

   → system/src/Grav/Common/Session.php

1. InstallCommand git clone shell injection — branch, url, and path values read from user/.dependencies are now passed through escapeshellarg, with a -- separator before url/path to block option-injection (e.g. --upload-pack=evil).  

   → system/src/Grav/Console/Cli/InstallCommand.php

1. SSTI blocklist bypass — twigarrayreduce (the specific name called out) plus twigarraysome and twigarrayevery added to cleanDangerousTwig's CALLABLEDANGEROUSNAMES alongside the existing twigarraymap/filter. More importantly, the new Twig content sandbox in 2.0.0-beta.2 blocks this class of attack at a different layer — see the sandbox work in 38685ac25.  

   → system/src/Grav/Common/Security.php

Tests:

• tests/unit/Grav/Common/Security/UnserializeIntegritySecurityTest.php — 8 cases covering JobQueue + Session HMAC integrity.
• tests/unit/Grav/Common/Security/FileCacheSecurityTest.php.
• tests/unit/Grav/Common/Security/CleanDangerousTwigTest.php — new twigarray* entries in providerCallbackFunctions.