CVE-2026-47863 Denial of service in Reactor Core
Attackers can cause permanent hangs in Reactor Core applications using bufferTimeout with fairBackpressure, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47863?
CVE-2026-47863 is a medium-severity denial of service vulnerability in Spring Reactor Core, published on 26 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In Reactor Core, applications that use the Flux.bufferTimeout operator with fairBackpressure enabled are vulnerable to a Denial of Service (DoS) condition. Reactor Core 3.8.0 - 3.8.6 Reactor Core 3.7.19 and earlier
Weakness: CWE-835
Which versions are affected by CVE-2026-47863?
It affects 1 product.
Products include Broadcom Reactor Core.
How do I fix CVE-2026-47863?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-47863 being exploited?
There is no known exploitation of CVE-2026-47863 in the wild and no public exploit code.
Other vulnerabilities in Spring Reactor Core
Sources
Also known as CLEANSTART-2026-BH93909, CLEANSTART-2026-VH51135, CLSA-2026-1792063063, CLSA-2026-1793138070, GHSA-5jp2-w3vg-5w3x.