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PHP CVE-2026-77138

| EUVDEUVD-2026-65338 CRITICAL
Deserialization of Untrusted Data (CWE-502)
2026-08-25 TYPO3 GHSA-mj2c-4qfw-rhhc
9.3
CVSS 4.0 · Vendor: TYPO3
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A08:2025 - Software or Data Integrity Failures
ASVS 5.0
V1 - Encoding and Sanitization Safe deserialization, type allowlists
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Initial Access

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 25, 2026

Remote code execution in the TYPO3 'HTML5 Video Player vs. Powermail' extension allows a remote, unauthenticated attacker to achieve arbitrary code execution on the server by supplying a crafted serialized value in an attacker-controlled cookie that is passed to PHP's unserialize(). The flaw is a classic PHP Object Injection (CWE-502) with full confidentiality, integrity, and availability impact and a CVSS 4.0 base score of 9.3. No public exploit identified at time of analysis, but the trivial attack requirements make weaponization straightforward.

Affected VersionsENISA

Extension "HTML5 Video Player vs. Powermail" 0 ≤0.2.1

Affected Packages

euvd extension_html5_video_player_vs_powermail no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (TYPO3) PRIMARY 9.3 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (TYPO3) · only source for this CVE.

CVSS VectorVendor: TYPO3

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
High
Vulnerable system: Availability
High
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

DescriptionCVE.org

The extension fails to safely process untrusted client input of an attacker-controlled cookie directly to PHP's unserialize(). A remote, unauthenticated attacker can supply a crafted serialized payload to trigger PHP Object Injection, leading to Remote Code Execution on the TYPO3 server.

Executive ViewAI

Why It Matters

A critical remote code execution vulnerability (CVE-2026-77138, CVSS 9.3) in the TYPO3 'HTML5 Video Player vs. Powermail' extension permits unauthenticated remote attackers to execute arbitrary code by injecting malicious serialized objects via cookies. Organizations deploying this extension face immediate risk of full system compromise, data exfiltration, and service unavailability. No vendor patch is currently available, requiring urgent containment measures.

Recommended Action

Within 24 hours, enumerate all TYPO3 instances running the 'HTML5 Video Player vs. Powermail' extension and determine operational criticality. Implement emergency mitigations: deploy Web Application Firewall rules to block cookie payloads containing serialized object patterns, restrict network access to affected instances to trusted IP ranges only, and enable detailed audit logging of cookie processing. Within 7 days, disable and uninstall the vulnerable extension from all systems where functionality permits, or air-gap affected TYPO3 instances from untrusted networks. Contact TYPO3 vendor for patch timeline and advisory updates. Within 30 days, apply vendor-released patch immediately upon availability, conduct forensic review of access logs and PHP execution logs for exploitation indicators, and implement application-level hardening to eliminate unserialize() usage on untrusted input.

Business Impact: Severe
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: (1) Immediately uninstall the TYPO3 'HTML5 Video Player vs. Powermail' extension if operationally feasible; (2) Deploy WAF rules blocking cookie values containing PHP serialized object signatures; (3) Implement network segmentation isolating TYPO3 instances from sensitive systems; (4) Enforce PHP configuration hardening (disable dangerous functions, restrict serialization handlers); (5) Deploy real-time alerting on cookie processing anomalies; (6) Monitor TYPO3 security advisories for emergency patch release.

Threat Intelligence Overview

EPSS Score
0.4%
Top 65% exploitable
Social Media
1
Sightings
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 0.4%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Out-of-Cycle
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
Very High
Technical Impact
Total

Priority Score

46
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +46
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Insecure deserialization occurs when an application converts serialized data (a stream of bytes representing an object's state) back into a living object without proper validation.

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

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