Denial of Service in MISP-STIX Import via Malformed or Oversized STIX Documents in misp-stix library

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-77755
StatePUBLISHED
AssignerCIRCL
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-21 10:16:39 UTC
Updated2026-08-21 12:16:36 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v4.0 8.7 HIGH from 5a6e4751-2f3f-4070-9419-94fb35b644e8

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-400 | CWE-400 CWE-400 Uncontrolled Resource Consumption

VersionSourceTypeScoreSeverityVector
4.05a6e4751-2f3f-4070-9419-94fb35b644e8Secondary8.7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/C...
4.0CNACVSS8.7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
High
Sub Conf.
None
Sub Integrity
None
Sub Availability
Low

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Misp Misp-stix affected 2026.7.8 semver Not specified

References

ReferenceSourceLinkTags
github.com/MISP/misp-stix/commit/e8e732ad 5a6e4751-2f3f-4070-9419-94fb35b644e8 github.com
github.com/MISP/misp-stix/commit/66119552 5a6e4751-2f3f-4070-9419-94fb35b644e8 github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Jeroen Pinoy (en)

CNA: Christian Studer (en)

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