GHSA-679F-58PQ-4V2C
Vulnerability from github – Published: 2026-09-10 21:05 – Updated: 2026-09-10 21:05Impact
The Instance AI workflow summary built its result with get-or-create-then-nested-write idioms keyed by node names and connection keys taken from the stored workflow. Those are arbitrary strings: the restricted-name guard n8n shows in the editor is client-side and is bypassed by posting the workflow to the REST API directly. So a reserved key such as __proto__ resolved up the prototype chain instead of creating an own key, and the write landed on Object.prototype in the main n8n process, affecting every later request. The patch builds the summary with null-prototype accumulators and validates the keys it accepts, so reserved names cannot reach the prototype chain.
Patches
The issue has been fixed in n8n versions 2.37.7 and 2.38.2. Users should upgrade to one of these versions or later to remediate the vulnerability.
Workarounds
If upgrading is not immediately possible, administrators should consider the following temporary mitigations:
- Restrict n8n instance access to fully trusted users only.
- Remove or leave unconfigured the N8N_INSTANCE_AI_MODEL* environment variables to prevent the Instance AI module from reaching the vulnerable code path.
- Restart the n8n process to clear any in-memory prototype pollution if an attack is suspected.
These workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "n8n"
},
"ranges": [
{
"events": [
{
"introduced": "2.38.0"
},
{
"fixed": "2.38.2"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "n8n"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.37.7"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-86078"
],
"database_specific": {
"cwe_ids": [
"CWE-1321"
],
"github_reviewed": true,
"github_reviewed_at": "2026-09-10T21:05:24Z",
"nvd_published_at": "2026-09-08T22:19:16Z",
"severity": "MODERATE"
},
"details": "## Impact\n\nThe Instance AI workflow summary built its result with get-or-create-then-nested-write idioms keyed by node names and connection keys taken from the stored workflow. Those are arbitrary strings: the restricted-name guard n8n shows in the editor is client-side and is bypassed by posting the workflow to the REST API directly. So a reserved key such as `__proto__` resolved up the prototype chain instead of creating an own key, and the write landed on `Object.prototype` in the main n8n process, affecting every later request. The patch builds the summary with null-prototype accumulators and validates the keys it accepts, so reserved names cannot reach the prototype chain.\n\n## Patches\n\nThe issue has been fixed in n8n versions 2.37.7 and 2.38.2. Users should upgrade to one of these versions or later to remediate the vulnerability.\n\n## Workarounds\n\nIf upgrading is not immediately possible, administrators should consider the following temporary mitigations:\n- Restrict n8n instance access to fully trusted users only.\n- Remove or leave unconfigured the `N8N_INSTANCE_AI_MODEL*` environment variables to prevent the Instance AI module from reaching the vulnerable code path.\n- Restart the n8n process to clear any in-memory prototype pollution if an attack is suspected.\n\nThese workarounds do not fully remediate the risk and should only be used as short-term mitigation measures.",
"id": "GHSA-679f-58pq-4v2c",
"modified": "2026-09-10T21:05:24Z",
"published": "2026-09-10T21:05:24Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/n8n-io/n8n/security/advisories/GHSA-679f-58pq-4v2c"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-86078"
},
{
"type": "PACKAGE",
"url": "https://github.com/n8n-io/n8n"
},
{
"type": "WEB",
"url": "https://github.com/n8n-io/n8n/releases/tag/n8n@2.37.7"
},
{
"type": "WEB",
"url": "https://github.com/n8n-io/n8n/releases/tag/n8n@2.38.2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "n8n: Prototype Pollution via Workflow Structure Summary Can Lead to Denial of Service"
}
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.
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.