CVE-2026-11525 (GCVE-0-2026-11525)

Vulnerability from cvelistv5 – Published: 2026-06-17 17:31 – Updated: 2026-06-17 17:54
VLAI
Title
undici vulnerable to Set-Cookie SameSite attribute downgrade via permissive substring matching
Summary
Impact: When 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). Affected 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. This was introduced in undici 5.15.0 when the cookies feature was added. Patches: Upgrade to undici v6.26.0, v7.28.0 or v8.5.0. Workarounds: After 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.
Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-183 - Permissive List of Allowed Inputs
Assigner
References
Impacted products
Vendor Product Version
undici undici Affected: 0 , < 6.26.0 (semver)
Unaffected: 6.26.0 (semver)
Affected: 7.0.0 , < 7.28.0 (semver)
Unaffected: 7.28.0 (semver)
Affected: 8.0.0 , < 8.5.0 (semver)
Unaffected: 8.5.0 (semver)
Create a notification for this product.
Credits
UlisesGascon KhafraDev mcollina tndud042713
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-11525",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-17T17:53:40.763762Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-17T17:54:22.022Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:npm/undici",
          "product": "undici",
          "vendor": "undici",
          "versions": [
            {
              "lessThan": "6.26.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.26.0",
              "versionType": "semver"
            },
            {
              "lessThan": "7.28.0",
              "status": "affected",
              "version": "7.0.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "7.28.0",
              "versionType": "semver"
            },
            {
              "lessThan": "8.5.0",
              "status": "affected",
              "version": "8.0.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "8.5.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "remediation reviewer",
          "value": "UlisesGascon"
        },
        {
          "lang": "en",
          "type": "remediation reviewer",
          "value": "KhafraDev"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "mcollina"
        },
        {
          "lang": "en",
          "type": "reporter",
          "value": "tndud042713"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "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\u0027s 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\u0027s view of a cookie\u0027s 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 \u0027Strict\u0027, \u0027Lax\u0027, or \u0027None\u0027 (exact, case-insensitive) before forwarding or relying on it."
            }
          ],
          "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\u0027s 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\u0027s view of a cookie\u0027s 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 \u0027Strict\u0027, \u0027Lax\u0027, or \u0027None\u0027 (exact, case-insensitive) before forwarding or relying on it."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 3.7,
            "baseSeverity": "LOW",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-183",
              "description": "CWE-183: Permissive List of Allowed Inputs",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-17T17:31:03.163Z",
        "orgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
        "shortName": "openjs"
      },
      "references": [
        {
          "url": "https://github.com/nodejs/undici/security/advisories/GHSA-g8m3-5g58-fq7m"
        },
        {
          "url": "https://cna.openjsf.org/security-advisories.html"
        }
      ],
      "title": "undici vulnerable to Set-Cookie SameSite attribute downgrade via permissive substring matching",
      "x_generator": {
        "engine": "cve-kit 1.0.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
    "assignerShortName": "openjs",
    "cveId": "CVE-2026-11525",
    "datePublished": "2026-06-17T17:31:03.163Z",
    "dateReserved": "2026-06-07T18:49:35.986Z",
    "dateUpdated": "2026-06-17T17:54:22.022Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-11525",
      "date": "2026-06-20",
      "epss": "0.00197",
      "percentile": "0.09571"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-11525\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-06-17T17:53:40.763762Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-06-17T17:53:46.041Z\"}}], \"cna\": {\"title\": \"undici vulnerable to Set-Cookie SameSite attribute downgrade via permissive substring matching\", \"credits\": [{\"lang\": \"en\", \"type\": \"remediation reviewer\", \"value\": \"UlisesGascon\"}, {\"lang\": \"en\", \"type\": \"remediation reviewer\", \"value\": \"KhafraDev\"}, {\"lang\": \"en\", \"type\": \"remediation developer\", \"value\": \"mcollina\"}, {\"lang\": \"en\", \"type\": \"reporter\", \"value\": \"tndud042713\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV3_1\": {\"version\": \"3.1\", \"baseScore\": 3.7, \"baseSeverity\": \"LOW\", \"vectorString\": \"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"undici\", \"product\": \"undici\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"6.26.0\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"6.26.0\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"7.0.0\", \"lessThan\": \"7.28.0\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"7.28.0\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"8.0.0\", \"lessThan\": \"8.5.0\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"8.5.0\", \"versionType\": \"semver\"}], \"packageURL\": \"pkg:npm/undici\", \"defaultStatus\": \"unaffected\"}], \"references\": [{\"url\": \"https://github.com/nodejs/undici/security/advisories/GHSA-g8m3-5g58-fq7m\"}, {\"url\": \"https://cna.openjsf.org/security-advisories.html\"}], \"x_generator\": {\"engine\": \"cve-kit 1.0.0\"}, \"descriptions\": [{\"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\u0027s 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\u0027s view of a cookie\u0027s 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 \u0027Strict\u0027, \u0027Lax\u0027, or \u0027None\u0027 (exact, case-insensitive) before forwarding or relying on it.\", \"supportingMedia\": [{\"type\": \"text/html\", \"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\u0027s 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\u0027s view of a cookie\u0027s 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 \u0027Strict\u0027, \u0027Lax\u0027, or \u0027None\u0027 (exact, case-insensitive) before forwarding or relying on it.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-183\", \"description\": \"CWE-183: Permissive List of Allowed Inputs\"}]}], \"providerMetadata\": {\"orgId\": \"ce714d77-add3-4f53-aff5-83d477b104bb\", \"shortName\": \"openjs\", \"dateUpdated\": \"2026-06-17T17:31:03.163Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-11525\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-06-17T17:54:22.022Z\", \"dateReserved\": \"2026-06-07T18:49:35.986Z\", \"assignerOrgId\": \"ce714d77-add3-4f53-aff5-83d477b104bb\", \"datePublished\": \"2026-06-17T17:31:03.163Z\", \"assignerShortName\": \"openjs\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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.


Detection rules are retrieved from Rulezet.