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    "cveMetadata": {
        "cveId": "CVE-2026-11525",
        "assignerOrgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
        "state": "PUBLISHED",
        "assignerShortName": "openjs",
        "dateReserved": "2026-06-07T18:49:35.986Z",
        "datePublished": "2026-06-17T17:31:03.163Z",
        "dateUpdated": "2026-06-17T17:54:22.022Z"
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                    "lang": "en",
                    "value": "Impact:\nWhen undici parses a Set-Cookie header, it accepts any SameSite attribute value that contains Strict, Lax, or None as a substring, rather than the case-insensitive exact match specified by RFC 6265. Non-spec values are silently mapped to one of the three standard tokens. For example, SameSite=NoneOfYourBusiness is parsed as None (the most permissive setting), and SameSite=StrictLax is parsed as Lax (a downgrade from Strict).\n\nAffected applications are those that consume Set-Cookie headers from server responses (for example via undici's fetch or proxy code paths) and then forward or rely on the parsed sameSite attribute. A malicious or non-compliant server can coerce the consumer's view of a cookie's SameSite policy to a weaker value, silently degrading the SameSite enforcement the cookie is supposed to provide.\n\nThis was introduced in undici 5.15.0 when the cookies feature was added.\n\nPatches:\nUpgrade to undici v6.26.0, v7.28.0 or v8.5.0.\n\nWorkarounds:\nAfter parsing a Set-Cookie header, validate that the resulting sameSite attribute is one of 'Strict', 'Lax', or 'None' (exact, case-insensitive) before forwarding or relying on it.",
                    "supportingMedia": [
                        {
                            "type": "text/html",
                            "base64": false,
                            "value": "Impact:\nWhen undici parses a Set-Cookie header, it accepts any SameSite attribute value that contains Strict, Lax, or None as a substring, rather than the case-insensitive exact match specified by RFC 6265. Non-spec values are silently mapped to one of the three standard tokens. For example, SameSite=NoneOfYourBusiness is parsed as None (the most permissive setting), and SameSite=StrictLax is parsed as Lax (a downgrade from Strict).\n\nAffected applications are those that consume Set-Cookie headers from server responses (for example via undici's fetch or proxy code paths) and then forward or rely on the parsed sameSite attribute. A malicious or non-compliant server can coerce the consumer's view of a cookie's SameSite policy to a weaker value, silently degrading the SameSite enforcement the cookie is supposed to provide.\n\nThis was introduced in undici 5.15.0 when the cookies feature was added.\n\nPatches:\nUpgrade to undici v6.26.0, v7.28.0 or v8.5.0.\n\nWorkarounds:\nAfter parsing a Set-Cookie header, validate that the resulting sameSite attribute is one of 'Strict', 'Lax', or 'None' (exact, case-insensitive) before forwarding or relying on it."
                        }
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                    "product": "undici",
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                            "versionType": "semver",
                            "status": "affected",
                            "version": "0",
                            "lessThan": "6.26.0"
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                            "version": "6.26.0"
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                            "version": "7.0.0",
                            "lessThan": "7.28.0"
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                            "versionType": "semver",
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                            "version": "8.5.0"
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                    "packageURL": "pkg:npm/undici"
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            ],
            "references": [
                {
                    "url": "https://github.com/nodejs/undici/security/advisories/GHSA-g8m3-5g58-fq7m"
                },
                {
                    "url": "https://cna.openjsf.org/security-advisories.html"
                }
            ],
            "credits": [
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                    "lang": "en",
                    "type": "remediation reviewer",
                    "value": "UlisesGascon"
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                    "type": "remediation reviewer",
                    "value": "KhafraDev"
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                    "type": "remediation developer",
                    "value": "mcollina"
                },
                {
                    "lang": "en",
                    "type": "reporter",
                    "value": "tndud042713"
                }
            ],
            "title": "undici vulnerable to Set-Cookie SameSite attribute downgrade via permissive substring matching",
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                        "baseScore": 3.7,
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                            "cweId": "CWE-183",
                            "lang": "en",
                            "description": "CWE-183: Permissive List of Allowed Inputs",
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                                "timestamp": "2026-06-17T17:53:40.763762Z",
                                "id": "CVE-2026-11525",
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                                        "Exploitation": "none"
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