Vulnerability-Lookup

FKIE_CVE-2026-73420

Vulnerability from fkie_nvd - Published: 2026-08-13 22:17 - Updated: 2026-09-18 20:05

Severity

9.1 (Critical) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Summary

NextAuth.js provides authentication for Next.js. Prior to @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32, the defaultNormalizer used by the email and magic-link sign-in flow validates an address before applying Unicode normalization. An address can contain a Unicode character such as U+FF20 FULLWIDTH COMMERCIAL AT that is not ASCII at-sign but canonicalizes to an ASCII at-sign under NFKC or NFKD normalization. The address passes the normalizer's single-at-sign check, but a downstream sendVerificationRequest mail library or delivery service that normalizes the address can then see two at-sign separators and deliver the passwordless sign-in link to an attacker-controlled recipient. Applications are affected when the email provider uses the built-in normalizer rather than a custom normalizeIdentifier and the downstream sender applies Unicode normalization. An attacker who knows a victim's email address can request the misrouted magic link and sign in as the victim without victim interaction. This issue is fixed in @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32.

References

	URL	Tags
	security-advisories@github.com	https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94
	security-advisories@github.com	https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0
	security-advisories@github.com	https://github.com/nextauthjs/next-auth/releases/tag/@auth/core@0.41.3
	security-advisories@github.com	https://github.com/nextauthjs/next-auth/releases/tag/next-auth@4.24.15
	security-advisories@github.com	https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32
	security-advisories@github.com	https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "next-auth",
          "vendor": "nextauthjs",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.24.15"
            },
            {
              "status": "affected",
              "version": "\u003e= 5.0.0-beta.4, \u003c 5.0.0-beta.32"
            }
          ]
        },
        {
          "product": "core",
          "vendor": "@auth",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 0.1.0, \u003c 0.41.3"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "NextAuth.js provides authentication for Next.js. Prior to @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32, the defaultNormalizer used by the email and magic-link sign-in flow validates an address before applying Unicode normalization. An address can contain a Unicode character such as U+FF20 FULLWIDTH COMMERCIAL AT that is not ASCII at-sign but canonicalizes to an ASCII at-sign under NFKC or NFKD normalization. The address passes the normalizer\u0027s single-at-sign check, but a downstream sendVerificationRequest mail library or delivery service that normalizes the address can then see two at-sign separators and deliver the passwordless sign-in link to an attacker-controlled recipient. Applications are affected when the email provider uses the built-in normalizer rather than a custom normalizeIdentifier and the downstream sender applies Unicode normalization. An attacker who knows a victim\u0027s email address can request the misrouted magic link and sign in as the victim without victim interaction. This issue is fixed in @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32."
    }
  ],
  "id": "CVE-2026-73420",
  "lastModified": "2026-09-18T20:05:53.723",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 9.1,
          "baseSeverity": "CRITICAL",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-73420",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-14T15:05:10.354847Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-13T22:17:26.297",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/nextauthjs/next-auth/releases/tag/@auth/core@0.41.3"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/nextauthjs/next-auth/releases/tag/next-auth@4.24.15"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-180"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

CVE-2026-73420 (GCVE-0-2026-73420)

Vulnerability from cvelistv5 – Published: 2026-08-13 22:04 – Updated: 2026-08-14 15:06

Title

NextAuth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass

Summary

Severity

9.1 (Critical)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-14 15:05 UTC

CWE

CWE-180 - Incorrect Behavior Order: Validate Before Canonicalize

Assigner

GitHub_M mitre root Scorecard

References

6 references

URL	Tags
https://github.com/nextauthjs/next-auth/security/…	x_refsource_CONFIRM
https://github.com/nextauthjs/next-auth/commit/19…	x_refsource_MISC
https://github.com/nextauthjs/next-auth/commit/a6…	x_refsource_MISC
https://github.com/nextauthjs/next-auth/releases/…	x_refsource_MISC
https://github.com/nextauthjs/next-auth/releases/…	x_refsource_MISC
https://github.com/nextauthjs/next-auth/releases/…	x_refsource_MISC

Impacted products

2 products

Vendor	Product	Version
nextauthjs	next-auth	Affected: < 4.24.15 Affected: >= 5.0.0-beta.4, < 5.0.0-beta.32
@auth	core	Affected: >= 0.1.0, < 0.41.3

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-73420",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-14T15:05:10.354847Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-14T15:06:00.594Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "next-auth",
          "vendor": "nextauthjs",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.24.15"
            },
            {
              "status": "affected",
              "version": "\u003e= 5.0.0-beta.4, \u003c 5.0.0-beta.32"
            }
          ]
        },
        {
          "product": "core",
          "vendor": "@auth",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 0.1.0, \u003c 0.41.3"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "NextAuth.js provides authentication for Next.js. Prior to @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32, the defaultNormalizer used by the email and magic-link sign-in flow validates an address before applying Unicode normalization. An address can contain a Unicode character such as U+FF20 FULLWIDTH COMMERCIAL AT that is not ASCII at-sign but canonicalizes to an ASCII at-sign under NFKC or NFKD normalization. The address passes the normalizer\u0027s single-at-sign check, but a downstream sendVerificationRequest mail library or delivery service that normalizes the address can then see two at-sign separators and deliver the passwordless sign-in link to an attacker-controlled recipient. Applications are affected when the email provider uses the built-in normalizer rather than a custom normalizeIdentifier and the downstream sender applies Unicode normalization. An attacker who knows a victim\u0027s email address can request the misrouted magic link and sign in as the victim without victim interaction. This issue is fixed in @auth/core 0.41.3 and next-auth 4.24.15 and 5.0.0-beta.32."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 9.1,
            "baseSeverity": "CRITICAL",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-180",
              "description": "CWE-180: Incorrect Behavior Order: Validate Before Canonicalize",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-13T22:04:15.414Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh"
        },
        {
          "name": "https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94"
        },
        {
          "name": "https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0"
        },
        {
          "name": "https://github.com/nextauthjs/next-auth/releases/tag/@auth/core@0.41.3",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/nextauthjs/next-auth/releases/tag/@auth/core@0.41.3"
        },
        {
          "name": "https://github.com/nextauthjs/next-auth/releases/tag/next-auth@4.24.15",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/nextauthjs/next-auth/releases/tag/next-auth@4.24.15"
        },
        {
          "name": "https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32"
        }
      ],
      "source": {
        "advisory": "GHSA-7rqj-j65f-68wh",
        "discovery": "UNKNOWN"
      },
      "title": "NextAuth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-73420",
    "datePublished": "2026-08-13T22:04:15.414Z",
    "dateReserved": "2026-08-12T14:32:11.795Z",
    "dateUpdated": "2026-08-14T15:06:00.594Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
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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 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.
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FKIE_CVE-2026-73420

CVE-2026-73420 (GCVE-0-2026-73420)

Tags

Sightings

Nomenclature

Related by attack behaviour