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Fencer Vulns
medium 5.9

CVE-2026-47863 json

Reactor Core bufferTimeout fair-backpressure pipeline permanently hangs when upstream delivers items during an active flush

published 2026-08-26 2 mo ago modified 2026-09-01 2 mo ago also EUVD-2026-66828

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

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

Patch / fix

  • broadcom reactor_core 3.7.20, 3.8.6.1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-47863 updated cvss 5.9

io.projectreactor/reactor-core: Reactor Core: Denial of Service in bufferTimeout operator

  • Red Hat Exploit Intelligence exploit-intelligence/agent-client-rhel9
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat build of Apache Camel 4 for Quarkus 3 reactor-core 3.7.11 Red Hat build of Debezium 3 reactor-core 3.7.11 Red Hat Data Grid 8 reactor-core 3.7.11
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Fuse 7 reactor-core 3.7.11
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat build of Quarkus 3.27.5.SP2
    fixed: vendor fix RHSA-2026:69470
  • Red Hat build of Quarkus 3.33.3.SP2
    fixed: vendor fix RHSA-2026:69440

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.40% chance of exploitation in the next 30 days, higher than 35% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Spring Reactor Core

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.