GCVE-1-2026-20174 (CVE-2026-77751)
Vulnerability from gna-1 – Published: 2026-08-21 09:48 – Updated: 2026-08-21 09:48
VLAI
EPSS
VEX
Title
Path Traversal in MISP Object Template Resolution During STIX Import and Export in misp-stix library
Summary
A path traversal vulnerability existed in the handling of MISP object template names during STIX 2 import and MISP-to-STIX 2 export.
MISP object names are passed to PyMISP's object-template resolution mechanism, which constructs a filesystem path by joining the configured MISP object-template directory, the object name, and definition.json. An object name originating from untrusted STIX or MISP content was not sufficiently restricted before being used in this filesystem path.
An attacker able to supply a crafted object name containing path separators or traversal sequences such as ../ could therefore cause template resolution to escape the expected template directory and attempt to load a definition.json file from another location accessible to the process.
During STIX 2 import, an attacker-controlled x_misp_name from a custom STIX object could directly reach this template-resolution mechanism.
The issue could also become persistent. A malicious object name stored in a MISP event could later be processed again during STIX 2 export. Consequently, content originally introduced in one security context could trigger filesystem access later when the event is exported by a process operating with different or greater privileges.
If a suitable definition.json file exists outside the intended template directory, its contents may be interpreted as a MISP object template and fields from that file copied into the converted object. This can result in unintended disclosure of locally accessible data represented by the template file and modification of the resulting object's metadata or semantics.
The patches introduce strict validation of object-template names. Valid names are restricted to a single path component containing letters, digits, hyphens, or underscores. Names that do not meet these requirements are replaced with the generic unknown-template name before reaching PyMISP template resolution. The original rejected name is preserved in the object's comment and a warning is generated, preventing traversal while retaining the source information.
Severity
CWE
- CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Assigner
References
2 references
Impacted products
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "misp-stix",
"repo": "https://github.com/MISP/misp-stix/",
"vendor": "misp",
"versions": [
{
"lessThanOrEqual": "2026.7.8",
"status": "affected",
"version": "0",
"versionType": "semver"
}
]
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],
"credits": [
{
"lang": "en",
"type": "remediation developer",
"value": "Christian Studer"
},
{
"lang": "en",
"type": "finder",
"value": "Jeroen Pinoy"
}
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"value": "\u003cp\u003eA path traversal vulnerability existed in the handling of MISP object template names during STIX 2 import and MISP-to-STIX 2 export.\u003c/p\u003e\u003cp\u003eMISP object names are passed to PyMISP\u0027s object-template resolution mechanism, which constructs a filesystem path by joining the configured MISP object-template directory, the object name, and \u003ccode\u003edefinition.json\u003c/code\u003e. An object name originating from untrusted STIX or MISP content was not sufficiently restricted before being used in this filesystem path.\u003c/p\u003e\u003cp\u003eAn attacker able to supply a crafted object name containing path separators or traversal sequences such as \u003ccode\u003e../\u003c/code\u003e could therefore cause template resolution to escape the expected template directory and attempt to load a \u003ccode\u003edefinition.json\u003c/code\u003e file from another location accessible to the process.\u003c/p\u003e\u003cp\u003eDuring \u003cstrong\u003eSTIX 2 import\u003c/strong\u003e, an attacker-controlled \u003ccode\u003ex_misp_name\u003c/code\u003e from a custom STIX object could directly reach this template-resolution mechanism.\u003c/p\u003e\u003cp\u003eThe issue could also become \u003cstrong\u003epersistent\u003c/strong\u003e. A malicious object name stored in a MISP event could later be processed again during STIX 2 export. Consequently, content originally introduced in one security context could trigger filesystem access later when the event is exported by a process operating with different or greater privileges.\u003c/p\u003e\u003cp\u003eIf a suitable \u003ccode\u003edefinition.json\u003c/code\u003e file exists outside the intended template directory, its contents may be interpreted as a MISP object template and fields from that file copied into the converted object. This can result in unintended disclosure of locally accessible data represented by the template file and modification of the resulting object\u0027s metadata or semantics.\u003c/p\u003e\u003cp\u003eThe patches introduce strict validation of object-template names. Valid names are restricted to a single path component containing letters, digits, hyphens, or underscores. Names that do not meet these requirements are replaced with the generic \u003ccode\u003eunknown-template\u003c/code\u003e name before reaching PyMISP template resolution. The original rejected name is preserved in the object\u0027s comment and a warning is generated, preventing traversal while retaining the source information.\u003c/p\u003e\u003cbr\u003e"
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"value": "A path traversal vulnerability existed in the handling of MISP object template names during STIX 2 import and MISP-to-STIX 2 export.\n\nMISP object names are passed to PyMISP\u0027s object-template resolution mechanism, which constructs a filesystem path by joining the configured MISP object-template directory, the object name, and definition.json. An object name originating from untrusted STIX or MISP content was not sufficiently restricted before being used in this filesystem path.\n\nAn attacker able to supply a crafted object name containing path separators or traversal sequences such as ../ could therefore cause template resolution to escape the expected template directory and attempt to load a definition.json file from another location accessible to the process.\n\nDuring STIX 2 import, an attacker-controlled x_misp_name from a custom STIX object could directly reach this template-resolution mechanism.\n\nThe issue could also become persistent. A malicious object name stored in a MISP event could later be processed again during STIX 2 export. Consequently, content originally introduced in one security context could trigger filesystem access later when the event is exported by a process operating with different or greater privileges.\n\nIf a suitable definition.json file exists outside the intended template directory, its contents may be interpreted as a MISP object template and fields from that file copied into the converted object. This can result in unintended disclosure of locally accessible data represented by the template file and modification of the resulting object\u0027s metadata or semantics.\n\nThe patches introduce strict validation of object-template names. Valid names are restricted to a single path component containing letters, digits, hyphens, or underscores. Names that do not meet these requirements are replaced with the generic unknown-template name before reaching PyMISP template resolution. The original rejected name is preserved in the object\u0027s comment and a warning is generated, preventing traversal while retaining the source information."
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"impacts": [
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"capecId": "CAPEC-126",
"descriptions": [
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"metrics": [
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"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
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"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 8.8,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
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"descriptions": [
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"description": "CWE-22 Improper Limitation of a Pathname to a Restricted Directory (\u0027Path Traversal\u0027)",
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"type": "CWE"
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"providerMetadata": {
"orgId": "00000000-0000-4000-9000-000000000000"
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"references": [
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"tags": [
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"url": "https://github.com/MISP/misp-stix/commit/a8b6808d"
},
{
"tags": [
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"url": "https://github.com/MISP/misp-stix/commit/a0f54070"
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"source": {
"discovery": "EXTERNAL"
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"title": "Path Traversal in MISP Object Template Resolution During STIX Import and Export in misp-stix library",
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"cveMetadata": {
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"cveId": "CVE-2026-77751",
"datePublished": "2026-08-21T09:48:06.996945Z",
"dateReserved": "2026-08-21T09:48:16.206Z",
"dateUpdated": "2026-08-21T09:48:16.277512Z",
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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