Description
A vulnerability in misp-stix could allow a crafted STIX document to influence security-sensitive MISP attribute metadata during import.

The STIX import logic automatically selected between the internal MISP parser and the external STIX parser based on metadata contained in the STIX document itself. For STIX2, the presence of MISP-specific tool labels could cause a document to be classified as originating from MISP; similarly, STIX1 relied on the document title. These classification indicators are fully controlled by the STIX producer and therefore cannot constitute a trusted indication of the document's origin. The accompanying fix explicitly notes that the parser choice was previously based solely on labels or header titles that any producer could write, and introduces an explicit classification parameter allowing callers to override this detection.

When STIX2 content was handled as an internal MISP export, attributes contained in an x-misp-object were converted by copying the complete x_misp_attributes dictionary and passing it directly to misp_object.add_attribute(). Consequently, a crafted STIX bundle could supply fields that were not part of the expected STIX-to-MISP round-trip format, including security-sensitive properties such as distribution, sharing_group_id, tags, or other MISP attribute fields.

An attacker able to provide a STIX document for import could therefore spoof the markers used to identify MISP-generated content and inject additional attribute properties. This could alter the distribution, sharing restrictions, classification, or semantic metadata of imported attributes, potentially causing information to be shared contrary to the importing organization's policy or influencing downstream processing and automation based on attacker-controlled tags or metadata.

The vulnerability results from dynamically assigning externally supplied object properties without restricting them to an expected set of attributes, matching CWE-915. MITRE specifically describes this weakness as accepting externally influenced fields without controlling which object attributes may be modified and recommends an allow-list, which is the approach implemented by the patch. The parser-selection issue additionally corresponds to CWE-807, because an untrusted value was used to make a security-relevant trust/classification decision.

The attack is also consistent with CAPEC-153 (Input Data Manipulation), in which an attacker controls the structure or flags of supplied data so that the target selects a different processing path or interprets the content differently than intended.
Published: 2026-08-21
Score: 6.9 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Unauthorized Attribute Metadata Modification
Action: Immediate Patch
AI Analysis

Impact

The misp-stix library selects between an internal MISP parser and an external STIX parser based on metadata that any STIX producer can control. A crafted STIX bundle can set MISP‑specific tool labels or a title to make the library believe the data is a native MISP export. As a result, the library mass‑assigns the entire x‑misp‑attributes dictionary to new attributes via misp_object.add_attribute(), allowing injection of security‑sensitive properties such as distribution, sharing_group_id, tags and other metadata. This can subvert an organization’s sharing policies and alter downstream processing and automation. The weakness is a classic input validation and property‑assignment flaw (CWE‑20).

Affected Systems

The vulnerability affects the MISP misp‑stix library. No specific version information is supplied, so all current releases of misp‑stix that accept STIX imports are potentially impacted.

Risk and Exploitability

The CVSS score is 6.9, indicating a moderate severity. EPSS data is unavailable and the vulnerability is not listed in the CISA KEV catalog. An attacker can remotely exploit the flaw by supplying a malicious STIX bundle to any endpoint that accepts imports. If the import interface is exposed to untrusted users, the vulnerability can be triggered without additional privileges.

Generated by OpenCVE AI on August 21, 2026 at 10:57 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Install the latest misp‑stix release that introduces an explicit classification parameter and restricts mass assignment to known safe fields.
  • Configure the system to use a fixed parser or supply an explicit classification flag instead of relying on document metadata when importing STIX bundles.
  • Restrict STIX import endpoints to authenticated, trusted users and validate incoming bundles against a whitelisted set of allowed fields to prevent injection of sensitive metadata.

Generated by OpenCVE AI on August 21, 2026 at 10:57 UTC.

Tracking

Sign in to view the affected projects.

Advisories

No advisories yet.

History

Fri, 21 Aug 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Fri, 21 Aug 2026 12:30:00 +0000

Type Values Removed Values Added
First Time appeared Misp
Misp misp-stix
Vendors & Products Misp
Misp misp-stix

Fri, 21 Aug 2026 09:00:00 +0000

Type Values Removed Values Added
Description A vulnerability in misp-stix could allow a crafted STIX document to influence security-sensitive MISP attribute metadata during import. The STIX import logic automatically selected between the internal MISP parser and the external STIX parser based on metadata contained in the STIX document itself. For STIX2, the presence of MISP-specific tool labels could cause a document to be classified as originating from MISP; similarly, STIX1 relied on the document title. These classification indicators are fully controlled by the STIX producer and therefore cannot constitute a trusted indication of the document's origin. The accompanying fix explicitly notes that the parser choice was previously based solely on labels or header titles that any producer could write, and introduces an explicit classification parameter allowing callers to override this detection. When STIX2 content was handled as an internal MISP export, attributes contained in an x-misp-object were converted by copying the complete x_misp_attributes dictionary and passing it directly to misp_object.add_attribute(). Consequently, a crafted STIX bundle could supply fields that were not part of the expected STIX-to-MISP round-trip format, including security-sensitive properties such as distribution, sharing_group_id, tags, or other MISP attribute fields. An attacker able to provide a STIX document for import could therefore spoof the markers used to identify MISP-generated content and inject additional attribute properties. This could alter the distribution, sharing restrictions, classification, or semantic metadata of imported attributes, potentially causing information to be shared contrary to the importing organization's policy or influencing downstream processing and automation based on attacker-controlled tags or metadata. The vulnerability results from dynamically assigning externally supplied object properties without restricting them to an expected set of attributes, matching CWE-915. MITRE specifically describes this weakness as accepting externally influenced fields without controlling which object attributes may be modified and recommends an allow-list, which is the approach implemented by the patch. The parser-selection issue additionally corresponds to CWE-807, because an untrusted value was used to make a security-relevant trust/classification decision. The attack is also consistent with CAPEC-153 (Input Data Manipulation), in which an attacker controls the structure or flags of supplied data so that the target selects a different processing path or interprets the content differently than intended.
Title STIX2 Parser Confusion and Mass Assignment Allow Unauthorized MISP Attribute Metadata Injection in misp-stix library
Weaknesses CWE-20
References
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N'}

Subscriptions

Misp Misp-stix
cve-icon MITRE

Status: PUBLISHED

Assigner: CIRCL

Published:

Updated: 2026-08-21T17:19:40.158Z

Reserved: 2026-08-21T08:53:55.657Z

Link: CVE-2026-77710

cve-icon Vulnrichment

Updated: 2026-08-21T17:18:52.798Z

cve-icon NVD

Status : Deferred

Published: 2026-08-21T09:16:41.027

Modified: 2026-08-26T16:49:18.760

Link: CVE-2026-77710

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-21T12:07:59Z

Weaknesses
  • CWE-20

    Improper Input Validation