CVE-2026-2836 Cache poisoning via insecure-by-default cache key

What is CVE-2026-2836?

CVE-2026-2836 is a high-severity vulnerability in https://github.com/cloudflare/pingora, published on 4 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official 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.

Weakness: CWE-345

Which versions are affected by CVE-2026-2836?

3 open source packages ship an affected version, including pingora-cache. It affects 1 product.

Products include Cloudflare Pingora.

How do I fix CVE-2026-2836?

Upgrade pingora-cache to 0.8.0 or later.

Is CVE-2026-2836 being exploited?

There is no known exploitation of CVE-2026-2836 in the wild and no public exploit code.

Other vulnerabilities in https://github.com/cloudflare/pingora

• CVE-2026-2833 HTTP Request Smuggling via Premature Upgrade Critical 9.3
• CVE-2026-2835 HTTP Request Smuggling via HTTP/1.0 and Transfer-Encoding Misparsing Critical 9.3
• CVE-2025-4366 Request Smuggling Vulnerability in Pingora High 7.4

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-f93w-pcj3-rggc, RUSTSEC-2026-0035.