CVE-2025-29904Network attack vector

Unauthenticated request smuggling via inconsistent HTTP parsing

Published Mar 12, 2025 · Updated Mar 12, 2025

HTTP request smuggling in JetBrains Ktor before 3.1.1 allows remote attackers to alter backend request interpretation. JetBrains has not disclosed the affected HTTP parser or the specific ambiguity that causes Ktor and an intermediary to disagree on request boundaries. Exploitation requires a network-reachable Ktor server behind an intermediary that parses a crafted request differently; no authentication or user interaction is required, and the published impact is limited to request integrity.

CVSS severity5.3
Medium
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request smuggling in JetBrains Ktor before 3.1.1 allows remote attackers to alter backend request interpretation. JetBrains has not disclosed the affected HTTP parser or the specific ambiguity that causes Ktor and an intermediary to disagree on request boundaries. Exploitation requires a network-reachable Ktor server behind an intermediary that parses a crafted request differently; no authentication or user interaction is required, and the published impact is limited to request integrity.

The record

CVE
CVE-2025-29904
Published
Mar 12, 2025
Updated
Mar 12, 2025
Vendor
JetBrains
Product
Ktor
Classifications
CWE-444, CAPEC-33, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Mar 12, 2025Record 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=0 <3.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

JetBrains · Ktorversion=0 <3.1.1

Published CVSS scores

5.3JetBrains s.r.o.CVSS: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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 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')
CAPEC-33HTTP Request Smuggling
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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