CVE-2025-26803Network attack vector

Service interruption via uninitialized parser pause state

Published Feb 24, 2025 · Updated Feb 24, 2025

Denial of service in Phusion Passenger 6.0.21 through 6.0.25 allows remote attackers to interrupt service with an invalid HTTP method. HttpHeaderParser returns an uninitialized pause-state flag after llhttp rejects the method, and its caller evaluates that flag while handling the parse error. No authentication or user interaction is required; published sources do not identify whether the interruption is a crash, hang, or another availability loss.

CVSS severity5.3
Medium
EPSS probability0.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Phusion Passenger 6.0.21 through 6.0.25 allows remote attackers to interrupt service with an invalid HTTP method. HttpHeaderParser returns an uninitialized pause-state flag after llhttp rejects the method, and its caller evaluates that flag while handling the parse error. No authentication or user interaction is required; published sources do not identify whether the interruption is a crash, hang, or another availability loss.

The record

CVE
CVE-2025-26803
Published
Feb 24, 2025
Updated
Feb 24, 2025
Vendor
Phusion
Product
Phusion Passenger
Classifications
CWE-908, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 24, 2025CVE publishedPublication date reported by the CVE source.
  2. Feb 24, 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=6.0.21 <6.0.26

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Phusion · Phusion Passengerversion=6.0.21 <6.0.26

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.3MITRECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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-908Use of Uninitialized Resource
T1499Endpoint Denial of Service

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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