CVE-2026-53666

mediumCVSS 6.1covered by 2 sourcesfirst seen 2026-07-23

If application code allows attacker supplied input to overwrite certain aspects of errors caught by the SSR process, then it was possible for attacker to trigger unexpected constructor execution on the client which would trigger outbound network traffic. This is only possible with very specific (and unlikely) application layer code. [!NOTE] This does not impact your application if you are using Declarative Mode. This only impacts Framework Mode and Data Mode applications doing manual SSR/hydration

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Exploitation outlook

Low exploitation risk0.42% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 34% of all EPSS-scored CVEs.

Advisory coverage (2)

mediumCVE-2026-53666: React Router is a router for React. In versions 6.4.0 through 7.17.0, if application code was …nvd · 2026-07-27
mediumGHSA-337j-9hxr-rhxg: React Router: Arbitrary Constructor Injection via deserializeErrors() in React Router SSR…ghsa · 2026-07-23

External references

NVD record for CVE-2026-53666

CVE.org record

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