CVE-2026-2833Public exploitNetwork attack vector

Request smuggling via premature upgrade passthrough

Published Mar 4, 2026 · Updated Mar 4, 2026

HTTP request smuggling in Cloudflare Pingora before 0.8.0 allows remote attackers to bypass proxy controls through upgrade requests. Pingora switches the connection to passthrough mode when it sees an Upgrade header and forwards buffered bytes before the backend returns 101 Switching Protocols. Exploitation requires a standalone Internet-facing Pingora ingress proxy and can poison a shared upstream connection, exposing another user's response or injecting a request past ACL and WAF checks.

CVSS severity9.3
Critical
EPSS probability0.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

HTTP request smuggling in Cloudflare Pingora before 0.8.0 allows remote attackers to bypass proxy controls through upgrade requests. Pingora switches the connection to passthrough mode when it sees an Upgrade header and forwards buffered bytes before the backend returns 101 Switching Protocols. Exploitation requires a standalone Internet-facing Pingora ingress proxy and can poison a shared upstream connection, exposing another user's response or injecting a request past ACL and WAF checks.

The record

CVE
CVE-2026-2833
Published
Mar 4, 2026
Updated
Mar 4, 2026
Vendor
Cloudflare
Product
Pingora
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 4, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=0 <0.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cloudflare · Pingoraversion=0 <0.8.0

Published CVSS scores

9.3Cloudflare, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N
9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 exploitPublished

Weakness, pattern, technique

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

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo