Security readout for executives and security teams
Plain-English summary
A flaw in certain Next.js App Router deployments can let an unauthenticated remote request bypass middleware-based protections, potentially exposing confidential information. Risk is highest where middleware.ts enforces authentication or access control and the application uses Turbopack. The supplied severity is High, with no user interaction required.
Executive priority
Treat this as an urgent patching item for public applications matching the affected configuration, especially where middleware protects sensitive customer, administrative, or tenant data. Rapidly identify exposed deployments and upgrade them. Lower priority only after configuration evidence shows the vulnerable middleware and Turbopack path is absent.
Technical view
CVE-2026-45109 is an incomplete fix for CVE-2026-44575 affecting middleware.ts under Turbopack. Segment-prefetch routes may avoid expected middleware processing in affected Next.js App Router applications. The supplied CVSS 3.1 score is 7.5, reflecting network reachability, low complexity, no privileges, and high confidentiality impact without stated integrity or availability impact.
Likely exposure
Prioritize internet-facing Next.js applications using affected 15.x or 16.x releases, the App Router, Turbopack, and middleware.ts for security decisions. Applications not using this combination may not be exploitable, but the supplied sources do not provide enough configuration detail to categorically exclude them.
Exploitation context
The source bundle marks this CVE as absent from CISA KEV, and no supplied source supports active exploitation. That does not establish that exploitation is impossible or has never occurred. The network-accessible, unauthenticated, low-complexity rating makes exposed vulnerable deployments attractive targets.
Researcher notes
The bundle contains a 15.x version inconsistency: its affected range ends before 15.5.17, while the description says releases before 15.5.18 are affected and names 15.5.18 as fixed. Conservatively treat 15.5.17 as potentially affected and use 15.5.18 or later unless Vercel clarifies otherwise. The stated 16.x fixed release is 16.2.6.
Mitigation direction
- Upgrade 15.x deployments to Next.js 15.5.18 or later.
- Upgrade 16.x deployments to Next.js 16.2.6 or later.
- Prioritize applications whose middleware enforces authentication, authorization, tenancy, or confidentiality boundaries.
- Consult the Vercel advisory for deployment-specific guidance and any subsequently published mitigations.
Validation and detection
- Inventory Next.js versions from manifests, lockfiles, build artifacts, and deployed application metadata.
- Confirm whether each application uses the App Router, Turbopack, and middleware.ts.
- Identify protected routes whose access decisions depend on middleware execution.
- After upgrading, run authorized regression tests confirming middleware protections apply across supported route and prefetch behavior.
- Review access logs for unexpected requests or responses involving protected App Router content.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-288: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-358: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-45109 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6GitHub_MCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6redhat-SADPVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- ADP timelineredhat-SADP
Made public.
- CVE publishedCVE Program
The CVE record was published.
- ADP timelineredhat-SADP
Reported to Red Hat.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-05-13T18:01:23.402Z: Reported to Red Hat.
- 2026-05-13T17:11:07.275Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/vercel/next.js/security/advisories/GHSA-26hh-7cqf-hhc6CVE reference, GitHub_M · x_refsource_CONFIRM
- https://access.redhat.com/security/cve/CVE-2026-45109CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2477190CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45109.jsonCVE reference, redhat-SADP · x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:40974CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:37272CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:34608CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:54435CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Authentication Bypass Using an Alternate Path or Channel
Authentication Bypass Using an Alternate Path or Channel represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improperly Implemented Security Check for Standard
Improperly Implemented Security Check for Standard represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.