CVE-2026-77710

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.5% 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 09:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-16 15:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.5% in the next 30 days (EPSS).
• Severity: 6.9 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-08-21 09:16 UTC

Last modified

2026-10-16 15:10 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-20 · Improper input validation

Record status

Deferred

Attack profile CVSS 4.0 · 6.9

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

None

Confidentiality

Low

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-77710.md and follow it. Check whether this project is affected by CVE-2026-77710. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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