CVE-2026-39555: Askka Deserialization Vulnerability

CVE-2026-39555 Overview

CVE-2026-39555 is a PHP Object Injection vulnerability affecting the Elated-Themes Askka WordPress theme through version 1.3.1. The flaw stems from unsafe deserialization of untrusted data [CWE-502], allowing attackers to inject crafted serialized PHP objects. Successful exploitation can lead to arbitrary code execution, file manipulation, or full site compromise when a vulnerable PHP magic method gadget chain is present. The vulnerability is exploitable over the network without authentication or user interaction.

Critical Impact
An unauthenticated remote attacker can inject malicious PHP objects into the Askka theme, potentially leading to arbitrary code execution and complete WordPress site takeover.

Affected Products

Elated-Themes Askka WordPress theme
Askka versions from n/a through 1.3.1
WordPress installations using the Askka theme

Discovery Timeline

2026-06-02 - CVE-2026-39555 published to NVD
2026-06-02 - Last updated in NVD database

Technical Details for CVE-2026-39555

Vulnerability Analysis

The Askka theme passes attacker-controlled input to a PHP deserialization function such as unserialize() without prior validation. When PHP deserializes data, it instantiates objects and invokes magic methods like __wakeup(), __destruct(), or __toString(). An attacker who supplies a crafted serialized payload can therefore trigger code paths in any class loaded at runtime, including classes provided by WordPress core, other plugins, or the theme itself.

The issue is classified under [CWE-502] Deserialization of Untrusted Data. The Patchstack advisory tracks the flaw as a PHP Object Injection issue, which historically enables file deletion, arbitrary file read or write, and remote code execution when a usable gadget chain is available in the target environment.

Root Cause

The root cause is the use of unsanitized input as the argument to PHP's deserialization routine. The theme does not enforce type checks, allow-lists of expected classes (allowed_classes parameter), or integrity validation such as a signed payload before reconstructing PHP objects from external data.

Attack Vector

The vulnerability is exploitable remotely over the network. An attacker submits a crafted serialized PHP payload to an exposed endpoint provided by the Askka theme. Exploitation does not require authentication or user interaction, although the higher attack complexity reflects the need to chain the injection with a usable gadget in the WordPress runtime to achieve impact.

No verified public proof-of-concept code is available. Technical details are documented in the Patchstack WordPress Vulnerability Report.

Detection Methods for CVE-2026-39555

Indicators of Compromise

HTTP requests containing serialized PHP markers such as O:, a:, or s: in parameters processed by the Askka theme.
Unexpected PHP processes spawned by the web server user, or new PHP files appearing in wp-content/themes/askka/ or wp-content/uploads/.
Outbound network connections from the WordPress host to unfamiliar IPs shortly after suspicious POST requests.
WordPress administrator accounts or options modified without a corresponding authenticated session.

Detection Strategies

Inspect web server access logs for POST or GET parameters containing PHP serialization patterns directed at Askka theme endpoints.
Enable PHP error and audit logging to capture calls to unserialize() on unexpected input and warnings about unknown class instantiation.
Deploy a Web Application Firewall (WAF) rule set that blocks serialized PHP payloads in request bodies and query strings.

Monitoring Recommendations

Monitor file integrity for the wp-content/themes/askka/ directory and core WordPress files, alerting on unauthorized changes.
Track creation of new admin users, plugin installations, and modifications to wp_options outside maintenance windows.
Centralize WordPress, PHP, and web server logs in a SIEM and correlate unauthenticated POST requests with subsequent file or process changes.

How to Mitigate CVE-2026-39555

Immediate Actions Required

Identify all WordPress sites running the Askka theme and confirm the installed version against 1.3.1 or earlier.
Apply the vendor-supplied patched release as soon as it is available, or deactivate and remove the Askka theme if no fix is published.
Restrict access to WordPress administrative endpoints and theme-handled routes using IP allow-lists or authentication where feasible.
Audit the host for indicators of compromise, including unexpected admin users, modified core files, and unfamiliar scheduled tasks.

Patch Information

No fixed version is listed in the NVD record at publication. Refer to the Patchstack WordPress Vulnerability Report for updated patch status and remediation guidance from Elated-Themes.

Workarounds

Disable the Askka theme and switch to a maintained, supported theme until a fixed version is released.
Deploy WAF signatures that block serialized PHP object payloads (for example, request bodies matching O:\d+:").
Harden PHP by disabling unnecessary functions and ensuring allowed_classes constraints are enforced in custom deserialization code.
Maintain offline backups of the WordPress database and wp-content directory to enable rapid recovery if compromise is detected.

bash

# Example WAF rule (ModSecurity) to block serialized PHP object payloads
SecRule ARGS|REQUEST_BODY "@rx O:\d+:\"[A-Za-z_\\\\]+\":\d+:" \
  "id:1026039555,phase:2,deny,status:403,log,\
   msg:'Potential PHP Object Injection (CVE-2026-39555)'"