CVE-2026-47857— Reactor Core windowTimeout fair-backpressure stream hang due to 20-bit index wrap-around
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.
在 Reactor Core 中，启用了公平背压（fairBackpressure）并使用 操作符的应用程序易受拒绝服务（DoS）问题影响。 受影响的版本： Reactor Core 3.8.0 - 3.8.6 Reactor Core 3.5.0 - 3.7.19 Reactor Core 3.4.41 及更早版本
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2026-47857
Vulnerability Information
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Vulnerability Title
Reactor Core windowTimeout fair-backpressure stream hang due to 20-bit index wrap-around
Source: CVE Program / CVE List V5
Vulnerability Description
In Reactor Core, applications that use the Flux.windowTimeout operator with fairBackpressure enabled are vulnerable to a Denial of Service (DoS) condition.
Reactor Core 3.8.0 - 3.8.6
Reactor Core 3.5.0 - 3.7.19
Reactor Core 3.4.41 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
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Spring | Reactor Core | 3.8.0 ~ 3.8.6 | - |
|
II. Public POCs for CVE-2026-47857
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Pages for CVE-2026-47857 (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-2026-47860 | 6.5 MEDIUM | Unbounded decompression of attacker-supplied compressed message bodies |
| CVE-2026-47842 | 6.5 MEDIUM | Deterministic AES/CBC Encryption in Spring Security AesBytesEncryptor Allows Ciphertext Co |
| CVE-2026-47856 | 6.3 MEDIUM | JsonToObjectTransformer resolves the json__TypeId__ message header to an arbitrary class w |
| CVE-2026-47861 | 6.3 MEDIUM | UDP adapter sends ack to attacker-supplied host:port parsed from packet body, even when ac |
| CVE-2026-47848 | 6.1 MEDIUM | Reactor Netty WebSocket Client Leaks Credentials On Redirect |
| CVE-2026-47863 | 5.9 MEDIUM | Reactor Core bufferTimeout fair-backpressure pipeline permanently hangs when upstream deli |
| 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-2026-47845 | 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-2026-47844 | 5.3 MEDIUM | Reactor Netty HTTP Server Leaks Exception Details |
| 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 vendor: Spring
-
CVE-2026-47874
Reactor Netty HTTP Server Denial of Service With Pipelined R -
CVE-2026-47861
UDP adapter sends ack to attacker-supplied host:port parsed -
CVE-2026-47863
Reactor Core bufferTimeout fair-backpressure pipeline perman -
CVE-2026-47862
ZipTransformer uses file_name header to build workDirectory -
CVE-2026-47860
Unbounded decompression of attacker-supplied compressed mess
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