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CVE-2026-123801supertokens supertokens-core capture-replay

Schedule itHigh7.4EPSS not scored yet

CVE-2026-123801 is a capture-replay in supertokens supertokens-core, rated high (7.4 on CVSS 3.1).

Why this priority: High severity, with no exploitation signal yet.

Published · Updated · NVD status: Received

What it is

A captured sign-in message can be replayed to authenticate again. The software does not check where a request or message really comes from.

How it is reached

An attacker can exploit it over the network, without an account, and nobody has to click anything. Success also depends on conditions the attacker does not fully control.

What an attacker gains

A successful attack can read the data it protects and change data or behaviour. In practice, this kind of flaw lets an attacker act as a signed-in user, or an administrator, without valid credentials.

Is it being exploited?

There is no public report of exploitation yet.

What to do

  1. Upgrade supertokens supertokens-core to a fixed version for your release line (11.3.8, 11.4.8, 12.0.11).
  2. Until it is patched, keep it off the internet or behind a VPN, allowlist or authenticating proxy.

Description from NVD

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 this means for your architecture.

A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.

Components it touches

  • Sign-in, session and token handling. The flaw sits between anonymous callers and authenticated sessions.
  • Identity providers and SSO. The flaw sits between anonymous callers and authenticated sessions.
  • Web front ends and single-page apps. The flaw sits between a user's browser and the web application.
  • Admin consoles served to a browser. The flaw sits between a user's browser and the web application.

Trust boundaries in play

  • Internet-facing entry points. No account is needed. Any instance reachable from outside your perimeter, through a load balancer, gateway, VPN or exposed admin port, is in scope.
  • Between anonymous callers and authenticated sessions. An attacker who crosses it can act as a signed-in user, or an administrator, without valid credentials.
  • Between a user's browser and the web application. An attacker who crosses it can act inside a signed-in user's browser session.

Questions to answer about your own systems

  • Where does supertokens supertokens-core run in your systems, and at which version?
  • Which of those instances can be reached from the internet or partner networks?
  • What can it reach once compromised: which data stores, secrets and services?
See how Veriom maps an architectureTake the interactive tour

Read more

Sources

  • CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
  • Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
  • Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
  • Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.