CVE-2026-40155: The Auth0 Next.js SDK is a library for implementing user authentication in Next.js applications

Q: How do I fix CVE-2026-40155?

nextjs-auth0: upgrade to 4.18.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-40155 being exploited?

CVE-2026-40155 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-40155 affect?

CVE-2026-40155 affects nextjs-auth0. Severity is medium (CVSS 5.4). 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 looku

Q: How urgent is CVE-2026-40155?

Priority 22/100. No elevated risk signals yet.

Routine

MEDIUM 5.4UPGRADE

CVE-2026-40155 is a medium-severity flaw (CVSS 5.4) affecting nextjs-auth0. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.2% (top 88%)
CISA exploited list	No
Weakness	CWE-362, CWE-863
Published	2026-04-17
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: auth0

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-17 21:16 UTCPublished CVE record published
2026-06-17 10:44 UTCUpdated Record last modified

auth0 nextjs-auth0 UPGRADE

Affected: >= 4.12.0 and < 4.18.0

Fixed in: 4.18.0

Safe to downgrade to: a release before 4.12.0

1. Check installed version

npm ls nextjs-auth0

2. UPGRADE to 4.18.0

npm install nextjs-auth0@">=4.18.0"

3. If no update is available yet, DOWNGRADE to a release before 4.12.0

npm view nextjs-auth0 versions npm install nextjs-auth0@"<4.12.0"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40155?

nextjs-auth0: upgrade to 4.18.0. Exact commands for each OS are on this page.

Is CVE-2026-40155 being exploited?

CVE-2026-40155 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40155 affect?

CVE-2026-40155 affects nextjs-auth0. Severity is medium (CVSS 5.4). 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 looku

How urgent is CVE-2026-40155?

Priority 22/100. No elevated risk signals yet.

Software pages

Auth0 vulnerabilities · Next.js vulnerabilities

References

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