CVE-2026-47857
Reactor Core windowTimeout fair-backpressure stream hang due to 20-bit index wrap-around
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
INFO
Published Date :
Aug. 27, 2026, 1:17 a.m.
Last Modified :
Sept. 4, 2026, 8:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | dcf2e128-44bd-42ed-91e8-88f912c1401d | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE |
Solution
- Update Reactor Core to version 3.8.7 or later.
- Update Reactor Core to version 3.7.20 or later.
- Update Reactor Core to a version after 3.4.41.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-47857.
| URL | Resource |
|---|---|
| https://spring.io/security/cve-2026-47857 | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-47857 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-47857
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-47857 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-47857 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Sep. 04, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:broadcom:reactor_core:*:*:*:*:*:*:*:* versions from (including) 3.8.0 up to (excluding) 3.8.6.1 *cpe:2.3:a:broadcom:reactor_core:*:*:*:*:*:*:*:* versions up to (excluding) 3.4.42 *cpe:2.3:a:broadcom:reactor_core:*:*:*:*:*:*:*:* versions from (including) 3.5.0 up to (excluding) 3.7.20 Added Reference Type VMware: https://spring.io/security/cve-2026-47857 Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 27, 2026
Action Type Old Value New Value Added CWE CWE-190 Added SSVC {'id': 'CVE-2026-47857', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-27T15:07:04.132397Z'} -
New CVE Received by [email protected]
Aug. 27, 2026
Action Type Old Value New Value Added 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 Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/47xxx/CVE-2026-47857.json">CVE-2026-47857</a> Added Reference https://spring.io/security/cve-2026-47857