CVE-2026-77755
HighCVSS 8.7Exploitation Probability (EPSS)
Low risk23th percentile - higher than 23% of all known CVEs
Summary
A denial-of-service vulnerability was identified in misp-stix when processing attacker-controlled STIX 1 or STIX 2 documents. The import code used sys.exit() to handle errors, causing unexpected process termination, and did not limit input size, leading to excessive memory and CPU consumption.
Risk Assessment
An attacker can terminate a long-running importer process, cause excessive resource consumption (memory, CPU), degrade or temporarily disable services relying on the converter, and disrupt batch or automated STIX ingestion workflows.
Recommendation
Update misp-stix to a patched version that replaces sys.exit() with catchable exceptions and enforces an input-size limit (default 100 MB). If updating is not possible, restrict access to STIX import functionality to trusted sources only.
Other vulnerabilities in misp-stix
See all- CVE-2026-77761Medium
A vulnerability in the misp-stix library stems from incomplete clearing of parser state between STIX document conversions. Reusing the same parser instance can cause data from a previously processed document (e.g., galaxies, DNS records, titles, timestamps) to be incorporated into the MISP event generated from a subsequent document. The issue affects both STIX 1 and STIX 2 parsers.
- CVE-2026-77710Medium
A vulnerability in misp-stix allows an attacker to supply a crafted STIX document that can influence security-sensitive MISP attribute metadata during import. The parser selection was based on untrusted indicators (tool labels or document title), enabling spoofing of MISP-origin content. Additionally, attributes from x-misp-object were copied without restrictions, allowing injection of unexpected fields.
Original NVD description (English source)
A denial-of-service vulnerability was identified in misp-stix when processing attacker-controlled STIX 1 or STIX 2 documents. The STIX import code used sys.exit() to handle several parsing and loading failures. Because SystemExit inherits from BaseException rather than Exception, these failures bypassed the exception handlers used by callers of the library. As a result, a malformed STIX document could terminate a long-running importer process instead of returning a recoverable parsing error. Additionally, no limit was imposed on the size of STIX documents before parsing. A submitted document was therefore read and materialised in memory before its validity or type was evaluated. Depending on the document and parsing path, processing could consume approximately two to seven times the input size in memory, allowing a sufficiently large STIX document to cause excessive memory and CPU consumption and potentially terminate or severely degrade the importing service. An attacker able to provide STIX content to a MISP-STIX import workflow could exploit either condition to affect availability. A malformed document could cause abnormal process termination through an uncaught SystemExit, while a large document could exhaust resources during deserialisation and conversion. The fixes replace process-terminating sys.exit() calls with catchable exceptions such as STIXLoadingError and MissingSTIXContentError, and extend exception handling around the complete STIX detection and conversion process. The importer also now enforces an input-size limit before parsing. The default maximum is 100 MB, can be adjusted by callers, and can explicitly be disabled when required. STIX 1 inputs are additionally checked for the expected root element before the complete XML tree is constructed. ImpactSuccessful exploitation can cause: * termination of a long-running MISP-STIX importer; * excessive memory allocation; * excessive CPU consumption; * degradation or temporary unavailability of services relying on the converter; * interruption of batch or automated STIX ingestion workflows.