CVE-2026-77710 (GCVE-0-2026-77710)

Vulnerability from cvelistv5 – Published: 2026-08-21 08:54 – Updated: 2026-08-21 17:19
VLAI
Title
STIX2 Parser Confusion and Mass Assignment Allow Unauthorized MISP Attribute Metadata Injection in misp-stix library
Summary
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.
Severity
6.9 (Medium)
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
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-21 17:18 UTC
CWE
  • CWE-20 - Improper Input Validation
Assigner
CIRCL CNA under the ENISA root
CNA scorecard B 90/100 over 236 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
MISP misp-stix Affected: 0 , ≤ 2026.7.8 (semver)
guessed Create a notification for this product.
Credits
Christian Studer 🕵️‍♂️ Jeroen Pinoy 🐞
Show details on NVD website
To clipboard 

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                  "value": "\u003cp\u003eA vulnerability in \u003cstrong\u003emisp-stix\u003c/strong\u003e could allow a crafted STIX document to influence security-sensitive MISP attribute metadata during import.\u003c/p\u003e\u003cp\u003eThe 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\u0027s 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 \u003ccode\u003eclassification\u003c/code\u003e parameter allowing callers to override this detection.\u003c/p\u003e\u003cp\u003eWhen STIX2 content was handled as an internal MISP export, attributes contained in an \u003ccode\u003ex-misp-object\u003c/code\u003e were converted by copying the complete \u003ccode\u003ex_misp_attributes\u003c/code\u003e dictionary and passing it directly to \u003ccode\u003emisp_object.add_attribute()\u003c/code\u003e. 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 \u003ccode\u003edistribution\u003c/code\u003e, \u003ccode\u003esharing_group_id\u003c/code\u003e, tags, or other MISP attribute fields.\u003c/p\u003e\u003cp\u003eAn 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\u0027s policy or influencing downstream processing and automation based on attacker-controlled tags or metadata.\u003c/p\u003e\u003cp\u003eThe vulnerability results from dynamically assigning externally supplied object properties without restricting them to an expected set of attributes, matching \u003cstrong\u003eCWE-915\u003c/strong\u003e. 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 \u003cstrong\u003eCWE-807\u003c/strong\u003e, because an untrusted value was used to make a security-relevant trust/classification decision.\u003c/p\u003e\u003cp\u003eThe attack is also consistent with \u003cstrong\u003eCAPEC-153 (Input Data Manipulation)\u003c/strong\u003e, 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.\u003c/p\u003e\u003cbr\u003e"
                }
              ],
              "value": "A vulnerability in misp-stix could allow a crafted STIX document to influence security-sensitive MISP attribute metadata during import.\n\nThe 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\u0027s 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.\n\nWhen 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.\n\nAn 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\u0027s policy or influencing downstream processing and automation based on attacker-controlled tags or metadata.\n\nThe 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.\n\nThe 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."
            }
          ],
          "impacts": [
            {
              "capecId": "CAPEC-153",
              "descriptions": [
                {
                  "lang": "en",
                  "value": "CAPEC-153 Input Data Manipulation"
                }
              ]
            }
          ],
          "metrics": [
            {
              "cvssV4_0": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "LOW",
                "attackRequirements": "NONE",
                "attackVector": "NETWORK",
                "baseScore": 6.9,
                "baseSeverity": "MEDIUM",
                "privilegesRequired": "NONE",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "valueDensity": "NOT_DEFINED",
                "vectorString": "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",
                "version": "4.0",
                "vulnAvailabilityImpact": "NONE",
                "vulnConfidentialityImpact": "LOW",
                "vulnIntegrityImpact": "LOW",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-20",
                  "description": "CWE-20 Improper Input Validation",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-21T08:54:01.414Z",
            "orgId": "5a6e4751-2f3f-4070-9419-94fb35b644e8",
            "shortName": "CIRCL"
          },
          "references": [
            {
              "tags": [
                "patch"
              ],
              "url": "https://github.com/MISP/misp-stix/commit/3e5e7bda"
            },
            {
              "tags": [
                "patch"
              ],
              "url": "https://github.com/MISP/misp-stix/commit/66c654b9"
            }
          ],
          "source": {
            "discovery": "EXTERNAL"
          },
          "title": "STIX2 Parser Confusion and Mass Assignment Allow Unauthorized MISP Attribute Metadata Injection in misp-stix library",
          "x_generator": {
            "engine": "Vulnogram 0.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "5a6e4751-2f3f-4070-9419-94fb35b644e8",
        "assignerShortName": "CIRCL",
        "cveId": "CVE-2026-77710",
        "datePublished": "2026-08-21T08:54:01.414Z",
        "dateReserved": "2026-08-21T08:53:55.657Z",
        "dateUpdated": "2026-08-21T17:19:40.158Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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