External risk intelligence

Movable Type Code Injection Vulnerability.

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-25776

Movable Type is a content management system designed to host websites and blogs. As a web-based platform, it is commonly deployed as an internet-facing application, making its management interfaces and public-facing content generation endpoints directly reachable from the internet in typical usage.

Code Injection

Sixapart Movable Type

2.14 and earlier9.0.59.0.69.1.08.0.2 to before 8.0.108.8.0 to before 8.8.39.0.1 to before 9.0.7

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified in Six Apart's Movable Type software, which is used for managing websites and blogs. This flaw allows for the injection of malicious code, potentially enabling unauthorized execution of commands on the affected systems. The main concern is to confirm if this specific software is in use within our environment.

Code injection flaw in content management software.
Confirms the relevance and potential exposure.
Assess internal use of Movable Type for risk.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted input to a Movable Type installation accessible over the internet. This input would target a code injection flaw within the application, potentially allowing the attacker to execute arbitrary Perl scripts. Successful exploitation could lead to significant compromise of the affected system, enabling the attacker to perform actions like reading sensitive data, modifying content, or even taking full control of the server.

No authentication or special access required.
Input processed by the application triggers vulnerability.
Arbitrary Perl script execution risk.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability in Movable Type could allow an unauthenticated attacker to inject and execute arbitrary Perl script when supported by the advisory. This could impact the integrity and availability of the system.

System data and service behavior.
Arbitrary Perl script execution.
Potential for system compromise.

Operational Fix

Recommended remediation, mitigation, and detection steps

Six Apart's Movable Type, a content management system, has a critical code injection vulnerability that could allow an attacker to execute arbitrary Perl scripts. This typically affects platform or application teams responsible for managing the Movable Type instances. The first practical step is to identify all deployed Movable Type instances, determine their network reachability, confirm business criticality, and then assign ownership for remediation planning.

Application owners should own the issue.
Verify instance reachability and business criticality.
Plan remediation based on assessed risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Movable Type?

Movable Type is a content management system developed by Six Apart Ltd. It is used to create and manage websites, blogs, and publishing platforms. Because it handles content and site structure, it often acts as the engine behind web publishing, requiring it to process various inputs to generate pages and manage site data.

What does this code injection vulnerability mean?

This flaw, classified as CWE-94, allows an unauthorized person to insert and run their own instructions within the application. Specifically for CVE-2026-25776, it targets the underlying Perl environment. Instead of just managing content, the software is tricked into executing unintended Perl scripts, which could give an attacker the same capabilities as the web server software itself.

How is this vulnerability triggered?

An attacker triggers this by sending specially crafted input to a vulnerable Movable Type instance. The flaw exists because the application processes this input incorrectly, allowing the execution of arbitrary commands. Critically, this does not require the attacker to have a pre-existing account or login credentials, as the software processes the malicious data directly through its standard communication channels.

Is my instance relevant to this threat?

Halo Surface Signal indicates that because Movable Type is designed to host web content, it is often deployed as an internet-facing application. If your instance is reachable from the internet, it is directly exposed to these malicious inputs. Internal-only instances are also affected, but those accessible from the open web face the most immediate risk of being targeted by unauthorized parties.

What is the first step to address CVE-2026-25776?

Begin by conducting a comprehensive inventory to identify all Movable Type instances across your environment. Once identified, map their network reachability to understand which ones face the internet. After establishing this, identify the internal teams responsible for each instance so that they can prioritize the systems for updates and coordinate the necessary patches provided by Six Apart.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.