What is the CVSS score of CVE-2026-2833?

CVE-2026-2833 has a CVSS 3.1 base score of 9.1 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. EPSS exploitation probability: 0.1%.

How to fix or mitigate CVE-2026-2833?

Within 24 hours: Inventory all systems running Pingora and assess exposure; enable enhanced monitoring for suspicious HTTP patterns. Within 7 days: Implement network segmentation to limit Pingora exposure; deploy WAF rules blocking malformed HTTP/1.1 upgrade requests; consider disabling HTTP upgrade functionality if not business-critical. Within 30 days: Prioritize vendor patch deployment immediately upon release; conduct forensic analysis for signs of exploitation.

Pingora CVE-2026-2833

CRITICAL

HTTP Request/Response Smuggling (CWE-444)

2026-03-05 cna@cloudflare.com

GHSA-xq2h-p299-vjwv

Code Injection Pingora Cloudflare

9.1

CVSS 3.1 · NVD

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Send HTTP request with Upgrade header
Delivery

Proxy forwards remaining bytes to backend prematurely
Exploit

Attacker injects malicious payload as subsequent request
Execution

Backend interprets payload as valid request header
Impact

Bypass security controls and hijack session

Vulnerability Assessment

Weakness	CWE CWE-444 OWASP Top 10:2025 A06:2025 - Insecure Design ASVS 5.0 V4 - API and Web Service HTTP request consistency
Exploitation Conditions	Pingora proxy configured to handle HTTP/1.1 connection upgrades without synchronizing upgrade acceptance with backend. Attacker requires network access to send HTTP requests to the proxy (AV:N/AC:L/PR:N/UI:N).
Impact	CVSS 9.1. Pingora is Cloudflare's Rust HTTP proxy.
Exploit ScenarioDerived	Smuggle requests through Pingora's upgrade handling.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

HTTP request smuggling in Cloudflare Pingora HTTP/1.1 upgrade handling.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 22:06 CVSS 9.1

HTTP smuggling in Cloudflare Pingora proxy.

RemediationAI

Update Pingora.

Affected Packages

cargo pingora-core fix: 0.8.0

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in cargo

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

CWE-444 HTTP request smuggling.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.1 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

CVE Published

Mar 05, 2026 - 00:15 nvd

CRITICAL 9.1

DescriptionCVE.org

An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.

Impact

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:

Bypass proxy-level ACL controls and WAF logic
Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests
Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP

Cloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.

Mitigation:

Pingora users should upgrade to Pingora v0.8.0 or higher

As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.

Executive ViewAI

Why It Matters

A critical HTTP request smuggling vulnerability in Pingora (CVSS 9.1) allows attackers to bypass security controls and potentially execute unauthorized actions. Organizations running Pingora are immediately at risk of data theft, session hijacking, and system compromise until patched or mitigated.

Business Impact: Severe

Compensating Controls

Disable HTTP/1.1 connection upgrade functionality if operationally feasible; implement WAF rules to reject malformed Upgrade headers and detect request smuggling patterns; apply network segmentation to limit Pingora exposure; increase logging and monitoring for anomalous HTTP traffic; consider traffic inspection at load balancer/reverse proxy layer to sanitize requests before reaching Pingora; maintain incident response readiness pending patch availability.

Threat Intelligence Overview

EPSS Score

0.1%

Top 80% exploitable

Data Quality

4 sources

Confidence: Medium

NVD

CVE.org

EPSS

GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV No

Public POC No

EPSS 0.1%

Patch available Yes

Active threat No

Deciding rule

CRITICAL severity

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Out-of-Cycle

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact

Very High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +46

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Code Injection CRITICAL

Code injection occurs when an application accepts user input and passes it directly into a language interpreter or evaluator without proper sanitization.