GHSA-337j-9hxr-rhxg: React Router: Arbitrary Constructor Injection via deserializeErrors() in React Router SSR Hydration
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
Details
Original advisory: https://github.com/advisories/GHSA-337j-9hxr-rhxg
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-536660.42% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 34% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-53666 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
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