CVE-2026-40155

Description

The Auth0 Next.js SDK is a library for implementing user authentication in Next.js applications. In versions 4.12.0 through 4.17.1, simultaneous requests that trigger a nonce retry may cause the proxy cache fetcher to perform improper lookups for the token request results. Users are affected if their project uses both the vulnerable versions and the proxy handler /me/* and /my-org/* with DPoP enabled. This issue has been fixed in version 4.18.0.

CVSS v3.1 Score

5.4

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:L/A:N

EPSS — Exploit Prediction

0.0006

Probability of exploitation

0.18%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-362 CWE-362

CWE-863 Incorrect Authorization

Affected Products

Vendor	Product	Versions
auth0	nextjs-auth0	4.12.0 — 4.18.0

References

Advisories & Patches

https://github.com/auth0/nextjs-auth0/commit/98c36dc306970c2230ea1a32efef431d29b99978 https://github.com/auth0/nextjs-auth0/security/advisories/GHSA-xq8m-7c5p-c2r6

Other References

https://github.com/auth0/nextjs-auth0/releases/tag/v4.18.0

Frequently Asked Questions

What is CVE-2026-40155? +

The Auth0 Next.js SDK is a library for implementing user authentication in Next.js applications. In versions 4.12.0 through 4.17.1, simultaneous requests that trigger a nonce retry may cause the proxy cache fetcher to perform improper lookups for the token request results. Users are affected if their project uses both the vulnerable versions and the proxy handler /me/* and /my-org/* with DPoP enabled. This issue has been fixed in version 4.18.0. It has a CVSS v3.1 base score of 5.4 (MEDIUM).

How severe is CVE-2026-40155? +

CVE-2026-40155 has a CVSS v3.1 score of 5.4 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0006, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-40155? +

CVE-2026-40155 affects products from auth0, specifically: nextjs-auth0. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-40155? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-41458

OwnTone Server versions 28.4 through 29.0 contain a race condition vulnerability in the DAAP login handler that allows unauthenticated attackers …

CVE-2026-43981

Algernon is a small self-contained pure-Go web server. Prior to 1.17.6, in engine/luahandler.go, the sync.RWMutex protecting LoadCommonFunctions is released before …

CVE-2026-42099

Sparx Pro Cloud Server is vulnerable to a Race Condition in the /data_api/dl_internal_artifact.php endpoint. The application downloads the properties of …

CVE-2025-0372

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in HYPR Passwordless on Windows allows Privilege Escalation.This issue …

CVE-2025-59052

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Angular uses a …

CVE-2024-47534

go-tuf is a Go implementation of The Update Framework (TUF). The go-tuf client inconsistently traces the delegations. For example, if …