Next.js Pages Router i18n Middleware Authorization Bypass
CVE-2026-44573 is a high-severity authorization bypass in Next.js affecting applications that use the Pages Router with i18n enabled and rely on middleware or proxy-based authorization. In affected versions, locale-less requests to the data route pattern /_next/data/<buildId>/<page>.json are not matched consistently with the corresponding localized page routes, so middleware does not execute for the unprefixed data request. As a result, an attacker can directly request the server-side rendered JSON data for protected pages without passing the intended authorization checks. The issue affects Next.js from 12.2.0 before 15.5.16, and the 16.x line before 16.2.5.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No valid public exploits. Mallory filtered out 1 candidate as fakes, detection scripts, or README-only repos.
All candidate exploits were filtered out by Mallory's validation.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.