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CVE-2026-47863— Reactor Core bufferTimeout fair-backpressure pipeline permanently hangs when upstream delivers items during an active flush

Quick assessment

Affected
Spring Reactor Core
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

VMware Reactor Core是美国VMware公司的一个基于响应式流规范的核心开发框架。 VMware Reactor Core 3.8.0版本至3.8.6版本和3.7.19及之前版本存在安全漏洞，该漏洞源于使用Flux.bufferTimeout操作符时启用了fairBackpressure，可能导致拒绝服务。

CVSS 5.9 · Medium EPSS 0.40% · P33

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 2

VendorProduct Version RangeStatus
Spring Reactor Core 3.8.0≤ 3.8.6 affected
≤ 3.7.19 affected
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I. Basic Information for CVE-2026-47863

Vulnerability Information
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Vulnerability Title
Reactor Core bufferTimeout fair-backpressure pipeline permanently hangs when upstream delivers items during an active flush
Source: CVE Program / CVE List V5
Vulnerability 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
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
VMware Reactor Core 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
VMware Reactor Core是美国VMware公司的一个基于响应式流规范的核心开发框架。 VMware Reactor Core 3.8.0版本至3.8.6版本和3.7.19及之前版本存在安全漏洞，该漏洞源于使用Flux.bufferTimeout操作符时启用了fairBackpressure，可能导致拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Spring Reactor Core 3.8.0 ~ 3.8.6 -

II. Public POCs for CVE-2026-47863

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III. Intelligence Information for CVE-2026-47863

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Vendor Pages for CVE-2026-47863 (1)

Same Patch Batch · Spring · 2026-08-26 · 20 CVEs total

CVE-2026-47852 7.5 HIGH Predictable cache directory location allows local ONNX model substitution in Spring AI
CVE-2026-47851 7.5 HIGH Unbounded recursion over attacker-controlled PDF outline tree in Spring AI PDF Document Re
CVE-2026-47841 7.4 HIGH WebAuthn User Verification Bypass via Session Serialization
CVE-2026-47836 7.2 HIGH Spring Cloud Config Server Susceptible To TOCTOU Attack When Using SVN
CVE-2026-47837 6.8 MEDIUM Spring Cloud Config Server Monitor Endpoint Does Not Validate Webhook Requests
CVE-2026-47842 6.5 MEDIUM Deterministic AES/CBC Encryption in Spring Security AesBytesEncryptor Allows Ciphertext Co
CVE-2026-47860 6.5 MEDIUM Unbounded decompression of attacker-supplied compressed message bodies
CVE-2026-47861 6.3 MEDIUM UDP adapter sends ack to attacker-supplied host:port parsed from packet body, even when ac
CVE-2026-47856 6.3 MEDIUM JsonToObjectTransformer resolves the json__TypeId__ message header to an arbitrary class w
CVE-2026-47848 6.1 MEDIUM Reactor Netty WebSocket Client Leaks Credentials On Redirect
CVE-2026-47857 5.9 MEDIUM Reactor Core windowTimeout fair-backpressure stream hang due to 20-bit index wrap-around
CVE-2026-47862 5.4 MEDIUM ZipTransformer uses file_name header to build workDirectory path without sanitization
CVE-2026-47859 5.4 MEDIUM Unbounded memory allocation in RFC6587SyslogDeserializer (octet-counted framing) — remote
CVE-2026-47844 5.3 MEDIUM Reactor Netty HTTP Server Leaks Exception Details
CVE-2026-47845 5.3 MEDIUM Reactor Netty HTTP Server may incorrectly evaluate proxy addresses
CVE-2026-47874 5.3 MEDIUM Reactor Netty HTTP Server Denial of Service With Pipelined Requests
CVE-2026-47834 4.8 MEDIUM Spring Data JPA Sort expression validation bypass
CVE-2026-47850 4.3 MEDIUM Spring Data REST allows mutation of the version property of immutable aggregates via PUT
CVE-2026-47843 3.7 LOW Reactor Netty may incorrectly route traffic due to DNS resolver reuse

IV. Related Vulnerabilities

Same product: Reactor Core
Same vendor: Spring

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