CVE-2026-77755: CWE-400 Uncontrolled Resource Consumption in misp misp-stix
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.
AI Analysis
Technical Summary
The vulnerability in misp-stix involves two main issues: first, the use of sys.exit() in the STIX import code to handle parsing failures, which raises SystemExit exceptions that bypass normal exception handlers and cause termination of long-running importer processes. Second, the absence of input size limits allows large STIX documents to be fully loaded into memory before validation, resulting in excessive memory and CPU usage. The fixes replace sys.exit() calls with catchable exceptions and add input size limits (default 100 MB) and root element checks for STIX 1 documents to prevent resource exhaustion and abnormal termination.
Potential Impact
Successful exploitation can cause termination of the MISP-STIX importer process, excessive memory allocation, high CPU consumption, degradation or temporary unavailability of services relying on the importer, and interruption of automated STIX ingestion workflows. This impacts availability and reliability of systems using misp-stix for STIX document processing.
Mitigation Recommendations
No official patch or remediation level is provided in the available data. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The described fixes involve replacing sys.exit() calls with catchable exceptions and enforcing input size limits before parsing. Until a fix is applied, consider restricting or validating STIX document inputs to prevent large or malformed documents from being processed.
CVE-2026-77755: CWE-400 Uncontrolled Resource Consumption in misp misp-stix
Description
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.
CVSS v4.0
Score 8.7high
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in misp-stix involves two main issues: first, the use of sys.exit() in the STIX import code to handle parsing failures, which raises SystemExit exceptions that bypass normal exception handlers and cause termination of long-running importer processes. Second, the absence of input size limits allows large STIX documents to be fully loaded into memory before validation, resulting in excessive memory and CPU usage. The fixes replace sys.exit() calls with catchable exceptions and add input size limits (default 100 MB) and root element checks for STIX 1 documents to prevent resource exhaustion and abnormal termination.
Potential Impact
Successful exploitation can cause termination of the MISP-STIX importer process, excessive memory allocation, high CPU consumption, degradation or temporary unavailability of services relying on the importer, and interruption of automated STIX ingestion workflows. This impacts availability and reliability of systems using misp-stix for STIX document processing.
Mitigation Recommendations
No official patch or remediation level is provided in the available data. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The described fixes involve replacing sys.exit() calls with catchable exceptions and enforcing input size limits before parsing. Until a fix is applied, consider restricting or validating STIX document inputs to prevent large or malformed documents from being processed.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- CIRCL
- Date Reserved
- 2026-08-21T09:55:04.399Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a882376acd9273b49f80ed0
Added to database: 08/21/2026, 10:07:50 UTC
Last enriched: 08/21/2026, 10:22:05 UTC
Last updated: 08/21/2026, 11:03:50 UTC
Views: 6
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