Security readout for executives and security teams
Plain-English summary
An unauthenticated internet attacker may take control of a TYPO3 server using a malicious cookie processed by the HTML5 Video Player vs. Powermail extension. Successful exploitation could expose data, alter content, disrupt service, and provide server-level code execution. The supplied record rates it critical at CVSS 9.3.
Executive priority
Treat as an immediate remediation priority for any confirmed affected, internet-facing TYPO3 server. Assign ownership today, establish the affected inventory, follow the vendor advisory, and investigate previously exposed systems. Systems without the named extension are not shown as affected by the supplied evidence.
Technical view
The extension passes attacker-controlled cookie data directly to PHP unserialize() without safe validation. This creates PHP Object Injection (CWE-502) and can result in remote code execution. The attack is network-accessible, low complexity, requires no privileges or user interaction, and has high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is limited to TYPO3 systems running lochmueller/html5videoplayer-powermail in the explicitly affected version listed as "0." The meaning and release scope of that version value are unclear from the bundle. Internet-reachable installations are the principal concern because exploitation requires no authentication.
Exploitation context
The supplied sources describe a remotely triggerable path through an attacker-controlled cookie. CVE-2026-77138 is not identified as a CISA KEV entry, and the bundle provides no evidence of active exploitation or public exploit availability. Absence from KEV does not establish that exploitation is impossible or absent.
Researcher notes
The reported sink is direct PHP unserialize() of untrusted cookie data, producing CWE-502 object injection. Actual code execution may depend on usable object classes in the application environment, but the CVE record states RCE impact. Exact affected-release interpretation, fixed versions, vendor mitigations, and exploitation telemetry are not included in the bundle.
Mitigation direction
- Inventory TYPO3 installations for lochmueller/html5videoplayer-powermail and record installed versions.
- Review the TYPO3 advisory for supported remediation, fixed versions, or extension removal guidance.
- Restrict public access to affected systems until vendor-directed remediation is completed.
- Preserve relevant web, application, and host logs before making operational changes.
Validation and detection
- Confirm the extension package name and installed version on every TYPO3 instance.
- Verify remediation against the TYPO3 advisory rather than assuming a version is safe.
- Review logs for unusual cookie values, PHP errors, unexpected processes, or unauthorized file changes.
- Reassess internet exposure and authentication boundaries after remediation.
- Run defensive integrity and compromise checks on previously exposed servers.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-502: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-77138 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.3 (4.0)
- Known Exploited
- No
- Published
Vector: 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
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
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——TYPO3Vulnerability scoring details
Base CVSS 4.0 score
9.3CriticalVector: 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
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://typo3.org/security/advisory/typo3-ext-sa-2026-014CVE reference, TYPO3 · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Deserialization of Untrusted Data
Deserialization of Untrusted Data represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.