CVE-2026-27977
Next.js is a React framework for building full-stack web applications.
Published Mar 18, 2026 · corrected/updated Jun 17, 2026 · vercel next.js · evidence confidence medium
Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, in , cross-site protection for internal websocket endpoints could treat as a bypass case even if is configured, allowing privacy-sensitive/opaque contexts (for example sandboxed documents) to connect unexpectedly. If a dev server is reachable from attacker-controlled content, an attacker may be able to connect to the HMR websocket channel and interact with dev websocket traffic. This affects development mode only. Apps without a configured still allow connections from any origin. The issue is fixed in version 16.1.7 by validating through the same cross-site origin-allowance checks used for other origins. If upgrading is not immediately possible, do not expose to untrusted networks and/or block websocket upgrades to when is at the proxy.
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-27977 is a low public vulnerability record for vercel next.js. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether vercel next.js is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: vercel/next.js. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 2.3. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-1385. Sources contributing to this record: cve_org, nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
Mar 18, 2026 · NIST NVD
Detected
Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, in , cross-site protection for internal websocket endpoints could treat as a bypass case even if is configured, allowing privacy-sensitive/opaque contexts (for example sandboxed documents) to connect unexpectedly. If a dev server is reachable from attacker-controlled conte
Jun 17, 2026 · NIST NVD
Updated
Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, in , cross-site protection for internal websocket endpoints could treat as a bypass case even if is configured, allowing privacy-sensitive/opaque contexts (for example sandboxed documents) to connect unexpectedly. If a dev server is reachable from attacker-controlled conte
Affected
- cpe vercel/next.jsversion unspecified
Sources
- CVE.orgVulnerability recordCVE-2026-27977
Official CVE identifier
cve.org - NIST NVDVulnerability recordCVE-2026-27977
Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, in , cross-site protection for internal websocket endpoints could treat as a bypass case even if is configur
nvd.nist.gov