CVE-2026-114139: Sentry-Javascript: Middleware Bypass when using Tunnel route

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.4%, percentile 34: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 34% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes @sentry/nextjs (npm) >= 9.36.0, < 9.47.2, fixed in 9.47.2; @sentry/nextjs (npm) >= 10.0.0-alpha.0, < 10.75.2, fixed in 10.75.2; @sentry/nextjs (npm) >= 11.0.0-alpha.0, < 11.0.0-rc.1, fixed in 11.0.0-rc.1. Check your lockfile, including transitive dependencies.

What it is

Sentry-Javascript is an official Sentry SDKs for JavaScript. From 9.36.0 until 9.47.2, 10.75.2, and 11.0.0-rc.1, the webpack integration for @sentry/nextjs skips application middleware for every request path under a configured tunnelRoute, while the tunnel rewrite serves only the exact tunnel path with valid o and p query parameters. When an application route directly collides with the tunnel path or a root dynamic segment resolves under it, an unauthenticated request can reach that route without middleware authorization. Exploitation requires tunnelRoute, a webpack build, a colliding route, and middleware being the only authorization control. This issue is fixed in versions 9.47.2, 10.75.2, and 11.0.0-rc.1.

From the GitHub advisory

Impact

The tunnelRoute option makes the SDK send browser events to a path on your own Next.js server (for example /monitoring), where a rewrite forwards them to Sentry to prevent ad blockers from blocking them. To keep those envelope requests from being rejected by your middleware, the SDK skips middleware for them.

The middleware skip was wider than the rewrite. The rewrite only serves requests to the tunnel path itself with the o and p parameters set. The skip applied to anything under the tunnel path. Requests in that gap go to your application instead of Sentry, and your middleware never runs on them.

Skipping middleware does not grant the request any privileges. Routes that check the session server-side are still protected.

You are affected only if all of the following are true:

Weakness type: CWE-693.

Product: @sentry/nextjs (npm) · Assigned by: GitHub_M · Published: 2026-10-21

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: present (depends on deployment conditions)
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• FIRST EPSS (model of 2026-10-22): 0.41% probability of exploitation activity in the next 30 days; percentile 34.

Timeline

• 2026-10-21 — CVE record last updated
• 2026-10-21 — CVE record published by GitHub_M
• 2026-10-22 — GitHub-reviewed advisory GHSA-mchm-gjx6-7h55 published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-mchm-gjx6-7h55 github.com
2. CVE.org record CVE-2026-114139 cve.org
3. NVD entry CVE-2026-114139 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
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10. github.com github.com

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