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CVE-2026-42342 is a high-severity denial-of-service vulnerability in React Router Framework Mode applications and Remix applications caused by unbounded path expansion in the internal __manifest endpoint. Affected versions are react-router 7.0.0 through 7.14.x and @remix-run/server-runtime 2.10.0 through 2.17.4. A remote attacker can send specially crafted HTTP requests that trigger disproportionate resource consumption during path processing for manifest handling, leading to algorithmic exhaustion of server CPU and/or memory. The issue affects server-side application deployments that expose the __manifest endpoint for route discovery and asset loading. Applications using Declarative Mode with <BrowserRouter> or Data Mode with createBrowserRouter and <RouterProvider> are not affected.
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What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
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No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
4 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A previously disclosed related vulnerability referenced as the precursor to CVE-2026-55685.
A denial-of-service vulnerability in React Router's manifest endpoint infrastructure that can exhaust server memory and cause service unavailability.
A high-severity denial-of-service vulnerability caused by unbounded path expansion in the __manifest endpoint of React Router Framework Mode and Remix v2 server-side rendering applications, allowing crafted HTTP requests to exhaust CPU and/or memory and make the application unavailable.
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.