CIRCL MISP up to 2026.7.8 STIX 2 Import Export definition.json path traversal

Summaryinfo

A vulnerability was found in CIRCL MISP up to 2026.7.8. It has been rated as critical. This issue affects some unknown processing of the file definition.json of the component STIX 2 Import Export. The manipulation leads to path traversal. This vulnerability is traded as CVE-2026-77751. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in CIRCL MISP up to 2026.7.8 and classified as critical. This issue affects an unknown function of the file definition.json of the component STIX 2 Import Export. The manipulation with an unknown input leads to a path traversal vulnerability. Using CWE to declare the problem leads to CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Impacted is confidentiality, integrity, and availability. The summary by CVE 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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-77751 since 08/21/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1006 according to MITRE ATT&CK.

By approaching the search of inurl:definition.json it is possible to find vulnerable targets with Google Hacking.

Applying the patch a8b6808d is able to eliminate this problem.

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Productinfo

Vendor

• CIRCL

Name

• MISP

Version

• 2026.7.0
• 2026.7.1
• 2026.7.2
• 2026.7.3
• 2026.7.4
• 2026.7.5
• 2026.7.6
• 2026.7.7
• 2026.7.8

License

• open-source

CPE 2.3info

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CPE 2.2info

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