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CVE-2026-34077 is a denial-of-service vulnerability in React Router affecting Framework Mode deployments that use Single Fetch, and associated Remix deployments using the same behavior. The flaw is caused by reflected user-controlled input reaching the server response encoding path and triggering expensive serialization work in the underlying data serialization algorithm. Under crafted conditions, this serialization becomes a performance bottleneck during encoding of certain server responses. The issue is limited to affected Framework Mode and Single Fetch configurations and does not affect applications operating in standard Declarative Mode. Some references also describe nearby RSC redirect-handling issues in unstable React Server Components APIs, but the available information for CVE-2026-34077 most consistently characterizes it as a server-side resource-consumption flaw tied to serialization overhead.
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6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A React Router vulnerability described as denial of service via client-side cross-site scripting in RSC redirect handling.
A denial-of-service vulnerability in React Router affecting applications in Framework Mode with Single Fetch enabled, where data serialization can cause backend crashes or stalls.
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.