CVE-2026-35209 (GCVE-0-2026-35209)
Vulnerability from cvelistv5
Published
2026-04-06 17:26
Modified
2026-04-06 18:49
Severity ?
VLAI Severity ?
EPSS score ?
CWE
- CWE-1321 - Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Summary
defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to `defu()` are vulnerable to prototype pollution. A crafted payload containing a `__proto__` key can override intended default values in the merged resul. The internal `_defu` function used `Object.assign({}, defaults)` to copy the defaults object. `Object.assign` invokes the `__proto__` setter, which replaces the resulting object's `[[Prototype]]` with attacker-controlled values. Properties inherited from the polluted prototype then bypass the existing `__proto__` key guard in the `for...in` loop and land in the final result. Version 6.1.5 replaces `Object.assign({}, defaults)` with object spread (`{ ...defaults }`), which uses `[[DefineOwnProperty]]` and does not invoke the `__proto__` setter.
References
| URL | Tags | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
||||||||||||||
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-35209",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-04-06T18:49:21.516737Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-04-06T18:49:29.040Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "defu",
"vendor": "unjs",
"versions": [
{
"status": "affected",
"version": "\u003c 6.1.5"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to `defu()` are vulnerable to prototype pollution. A crafted payload containing a `__proto__` key can override intended default values in the merged resul. The internal `_defu` function used `Object.assign({}, defaults)` to copy the defaults object. `Object.assign` invokes the `__proto__` setter, which replaces the resulting object\u0027s `[[Prototype]]` with attacker-controlled values. Properties inherited from the polluted prototype then bypass the existing `__proto__` key guard in the `for...in` loop and land in the final result. Version 6.1.5 replaces `Object.assign({}, defaults)` with object spread (`{ ...defaults }`), which uses `[[DefineOwnProperty]]` and does not invoke the `__proto__` setter."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-1321",
"description": "CWE-1321: Improperly Controlled Modification of Object Prototype Attributes (\u0027Prototype Pollution\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-04-06T17:26:52.975Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/unjs/defu/security/advisories/GHSA-737v-mqg7-c878",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/unjs/defu/security/advisories/GHSA-737v-mqg7-c878"
},
{
"name": "https://github.com/unjs/defu/pull/156",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/unjs/defu/pull/156"
},
{
"name": "https://github.com/unjs/defu/commit/3942bfbbcaa72084bd4284846c83bd61ed7c8b29",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/unjs/defu/commit/3942bfbbcaa72084bd4284846c83bd61ed7c8b29"
},
{
"name": "https://github.com/unjs/defu/releases/tag/v6.1.5",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/unjs/defu/releases/tag/v6.1.5"
}
],
"source": {
"advisory": "GHSA-737v-mqg7-c878",
"discovery": "UNKNOWN"
},
"title": "defu: Prototype pollution via `__proto__` key in defaults argument"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-35209",
"datePublished": "2026-04-06T17:26:52.975Z",
"dateReserved": "2026-04-01T18:48:58.937Z",
"dateUpdated": "2026-04-06T18:49:29.040Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"vulnrichment": {
"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-35209\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-04-06T18:49:21.516737Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-04-06T18:49:25.733Z\"}}], \"cna\": {\"title\": \"defu: Prototype pollution via `__proto__` key in defaults argument\", \"source\": {\"advisory\": \"GHSA-737v-mqg7-c878\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 7.5, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"NONE\"}}], \"affected\": [{\"vendor\": \"unjs\", \"product\": \"defu\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003c 6.1.5\"}]}], \"references\": [{\"url\": \"https://github.com/unjs/defu/security/advisories/GHSA-737v-mqg7-c878\", \"name\": \"https://github.com/unjs/defu/security/advisories/GHSA-737v-mqg7-c878\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"https://github.com/unjs/defu/pull/156\", \"name\": \"https://github.com/unjs/defu/pull/156\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/unjs/defu/commit/3942bfbbcaa72084bd4284846c83bd61ed7c8b29\", \"name\": \"https://github.com/unjs/defu/commit/3942bfbbcaa72084bd4284846c83bd61ed7c8b29\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/unjs/defu/releases/tag/v6.1.5\", \"name\": \"https://github.com/unjs/defu/releases/tag/v6.1.5\", \"tags\": [\"x_refsource_MISC\"]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to `defu()` are vulnerable to prototype pollution. A crafted payload containing a `__proto__` key can override intended default values in the merged resul. The internal `_defu` function used `Object.assign({}, defaults)` to copy the defaults object. `Object.assign` invokes the `__proto__` setter, which replaces the resulting object\u0027s `[[Prototype]]` with attacker-controlled values. Properties inherited from the polluted prototype then bypass the existing `__proto__` key guard in the `for...in` loop and land in the final result. Version 6.1.5 replaces `Object.assign({}, defaults)` with object spread (`{ ...defaults }`), which uses `[[DefineOwnProperty]]` and does not invoke the `__proto__` setter.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-1321\", \"description\": \"CWE-1321: Improperly Controlled Modification of Object Prototype Attributes (\u0027Prototype Pollution\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-04-06T17:26:52.975Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-35209\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-04-06T18:49:29.040Z\", \"dateReserved\": \"2026-04-01T18:48:58.937Z\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"datePublished\": \"2026-04-06T17:26:52.975Z\", \"assignerShortName\": \"GitHub_M\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
Loading…
Loading…