{"id":"CVE-2026-73420","state":"PUBLISHED","title":"NextAuth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass","description":"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.","publishedAt":"2026-08-13T22:04:15.414Z","updatedAt":"2026-08-14T15:06:00.594Z","severity":{"score":9.1,"label":"Critical","version":"4.0","vector":"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","source":"GitHub_M"},"assigner":"GitHub_M","products":["nextauthjs next-auth","@auth core"],"affected":[{"vendor":"nextauthjs","product":"next-auth","versions":[{"version":"< 4.24.15","status":"affected"},{"version":">= 5.0.0-beta.4, < 5.0.0-beta.32","status":"affected"}]},{"vendor":"@auth","product":"core","versions":[{"version":">= 0.1.0, < 0.41.3","status":"affected"}]}],"references":["https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh","https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94","https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0","https://github.com/nextauthjs/next-auth/releases/tag/@auth/core@0.41.3","https://github.com/nextauthjs/next-auth/releases/tag/next-auth@4.24.15","https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32"],"weaknesses":["CWE-180"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/73xxx/CVE-2026-73420.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-73420","state":"PUBLISHED","datePublished":"2026-08-13T22:04:15.414Z","dateUpdated":"2026-08-14T15:06:00.594Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-08-12T14:32:11.795Z"},"containers":{"cna":{"title":"NextAuth.js: Email normalizer validates the address before Unicode normalization, allowing a homoglyph @ bypass","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'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."}],"affected":[{"vendor":"nextauthjs","product":"next-auth","versions":[{"version":"< 4.24.15","status":"affected"},{"version":">= 5.0.0-beta.4, < 5.0.0-beta.32","status":"affected"}]},{"vendor":"@auth","product":"core","versions":[{"version":">= 0.1.0, < 0.41.3","status":"affected"}]}],"references":[{"url":"https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh","name":"https://github.com/nextauthjs/next-auth/security/advisories/GHSA-7rqj-j65f-68wh","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94","name":"https://github.com/nextauthjs/next-auth/commit/19d2feb24359fa8c79418907fc68d9ec8152ca94","tags":["x_refsource_MISC"]},{"url":"https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0","name":"https://github.com/nextauthjs/next-auth/commit/a63eee12a1a20cb35209e44195b097868517b9a0","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/@auth/core@0.41.3","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@4.24.15","tags":["x_refsource_MISC"]},{"url":"https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32","name":"https://github.com/nextauthjs/next-auth/releases/tag/next-auth@5.0.0-beta.32","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":9.1,"baseSeverity":"CRITICAL","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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-180","lang":"en","description":"CWE-180: Incorrect Behavior Order: Validate Before Canonicalize","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-13T22:04:15.414Z"},"source":{"advisory":"GHSA-7rqj-j65f-68wh","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-14T15:05:10.354847Z","id":"CVE-2026-73420","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-14T15:06:00.594Z"}}]}}}