CVE-2026-2836

High

Published: 05 March 2026

Published

05 March 2026

Modified

12 March 2026

KEV Added

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Patch

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CVSS Score 8.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

EPSS Score 0.0001 0.6th percentile

Risk Priority 16 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-2836 is a high-severity Insufficient Verification of Data Authenticity (CWE-345) vulnerability in Cloudflare Pingora. Its CVSS base score is 8.1 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 0.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 CM-6 (Configuration Settings) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 2 other techniques. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Directly requires timely remediation of known flaws like CVE-2026-2836 by upgrading Pingora to v0.8.0 or implementing custom cache keys to eliminate insecure defaults.

CM-6 Configuration Settings good match

prevent

Mandates secure configuration settings for HTTP proxy caches, ensuring cache keys incorporate host headers, schemes, and other factors to prevent poisoning and cross-tenant leakage.

CM-2 Baseline Configuration partial match

prevent

Establishes baseline configurations for caching proxies that exclude insecure default cache key implementations and enforce proper key construction parameters.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1189 Drive-by Compromise Initial Access

Adversaries may gain access to a system through a user visiting a website over the normal course of browsing.

attack.mitre.org →

T1565.002 Transmitted Data Manipulation Impact

Adversaries may alter data en route to storage or other systems in order to manipulate external outcomes or hide activity, thus threatening the integrity of the data.

attack.mitre.org →

Why these techniques?

Cache poisoning in public-facing HTTP proxy directly enables exploitation of the application (T1190) to manipulate served responses (T1565.002) and deliver malicious content via drive-by access (T1189).

Confidence: MEDIUM · MITRE ATT&CK Enterprise v18.1

NVD Description

A cache poisoning vulnerability has been found in the Pingora HTTP proxy framework’s default cache key construction. The issue occurs because the default HTTP cache key implementation generates cache keys using only the URI path, excluding critical factors such as…

the host header (authority). Operators relying on the default are vulnerable to cache poisoning, and cross-origin responses may be improperly served to users. Impact This vulnerability affects users of Pingora's alpha proxy caching feature who relied on the default CacheKey implementation. An attacker could exploit this for: * Cross-tenant data leakage: In multi-tenant deployments, poison the cache so that users from one tenant receive cached responses from another tenant * Cache poisoning attacks: Serve malicious content to legitimate users by poisoning shared cache entries Cloudflare's CDN infrastructure was not affected by this vulnerability, as Cloudflare's default cache key implementation uses multiple factors to prevent cache key poisoning and never made use of the previously provided default. Mitigation: We strongly recommend Pingora users to upgrade to Pingora v0.8.0 or higher, which removes the insecure default cache key implementation. Users must now explicitly implement their own callback that includes appropriate factors such as Host header, origin server HTTP scheme, and other attributes their cache should vary on. Pingora users on previous versions may also remove any of their default CacheKey usage and implement their own that should at minimum include the host header / authority and upstream peer’s HTTP scheme.

Deeper analysisAI

CVE-2026-2836 is a cache poisoning vulnerability in the Pingora HTTP proxy framework’s default cache key construction, published on 2026-03-05. The default HTTP cache key implementation generates keys using only the URI path, excluding critical factors such as the host header (authority). This affects users of Pingora's alpha proxy caching feature who rely on the default CacheKey implementation, potentially leading to improper serving of cross-origin responses.

The vulnerability has a CVSS score of 8.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N) and is associated with CWE-345. Remote attackers require no privileges but need user interaction to exploit it over the network with low complexity. Successful exploitation enables cross-tenant data leakage in multi-tenant deployments, where attackers poison the cache so users from one tenant receive cached responses from another, or cache poisoning attacks to serve malicious content to legitimate users.

Advisories recommend upgrading to Pingora v0.8.0 or higher, which removes the insecure default cache key implementation; users must then explicitly implement their own callback including the Host header (authority), origin server HTTP scheme, and other relevant attributes. On previous versions, users should remove any default CacheKey usage and implement a custom one that includes at minimum the host header/authority and upstream peer’s HTTP scheme. See the Pingora GitHub repository at https://github.com/cloudflare/pingora for details.

Cloudflare's CDN infrastructure was not affected, as its default cache key implementation uses multiple factors to prevent such poisoning and never relied on the provided default.