CVE-2026-77751

What it is

A path traversal vulnerability existed in the handling of MISP object template names during STIX 2 import and MISP-to-STIX 2 export. MISP object names are passed to PyMISP's object-template resolution mechanism, which constructs a filesystem path by joining the configured MISP object-template directory, the object name, and definition.json. An object name originating from untrusted STIX or MISP content was not sufficiently restricted before being used in this filesystem path. An attacker able to supply a crafted object name containing path separators or traversal sequences such as ../ could therefore cause template resolution to escape the expected template directory and attempt to load a definition.json file from another location accessible to the process. During STIX 2 import, an attacker-controlled x_misp_name from a custom STIX object could directly reach this template-resolution mechanism. The issue could also become persistent. A malicious object name stored in a MISP event could later be processed again during STIX 2 export. Consequently, content originally introduced in one security context could trigger filesystem access later when the event is exported by a process operating with different or greater privileges. If a suitable definition.json file exists outside the intended template directory, its contents may be interpreted as a MISP object template and fields from that file copied into the converted object. This can result in unintended disclosure of locally accessible data represented by the template file and modification of the resulting object's metadata or semantics. The patches introduce strict validation of object-template names. Valid names are restricted to a single path component containing letters, digits, hyphens, or underscores. Names that do not meet these requirements are replaced with the generic unknown-template name before reaching PyMISP template resolution. The original rejected name is preserved in the object's comment and a warning is generated, preventing traversal while retaining the source information.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure.

Exploit odds

0.7% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-21 10:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-16 15:10 UTC Last updatedMost recent change to the record

Details

Published

2026-08-21 10:16 UTC

Last modified

2026-10-16 15:10 UTC

Exploit probability

0.7% · EPSS, next 30 days

Weakness

CWE-22 · Path traversal

Record status

Deferred

Attack profile CVSS 4.0 · 8.8

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

None

Confidentiality

High

Integrity

Low

Availability

None