CVE-2026-41853Network attack vector

WAF bypass via multipart parser discrepancies

Published Jun 9, 2026 · Updated Jun 9, 2026

Multipart request smuggling in Spring Framework allows remote attackers to bypass WAF or proxy content checks with crafted requests. Spring has not disclosed the exact MVC or WebFlux parsing rule that interprets malicious multipart bodies differently from an upstream intermediary. Exposure requires multipart handling behind a WAF or proxy that parses and filters multipart content; successful requests reach application handling despite those checks.

CVSS severity5.3
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Multipart request smuggling in Spring Framework allows remote attackers to bypass WAF or proxy content checks with crafted requests. Spring has not disclosed the exact MVC or WebFlux parsing rule that interprets malicious multipart bodies differently from an upstream intermediary. Exposure requires multipart handling behind a WAF or proxy that parses and filters multipart content; successful requests reach application handling despite those checks.

The record

CVE
CVE-2026-41853
Published
Jun 9, 2026
Updated
Jun 9, 2026
Vendor
Spring
Product
Spring Framework
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.3.0 <5.3.49
  2. Affected versionversion=6.1.0 <6.1.28
  3. Affected versionversion=6.2.0 <6.2.19
  4. Affected versionversion=7.0.0 <7.0.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Spring · Spring Frameworkversion=5.3.0 <5.3.49; version=6.1.0 <6.1.28; version=6.2.0 <6.2.19; version=7.0.0 <7.0.8

Published CVSS scores

5.3VMwareCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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