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

2026-10-02T23:50:02.551068+00:00

Affected: Cloudflare https://github.com/cloudflare/pingora

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 def…

GHSA-f93w-pcj3-rggc — Pingora vulnerable to cache poisoning via insecure-by-default cache key

2026-10-02T23:50:02.551161+00:00

Affected: crates.io: pingora-cache

### Impact Pingora versions prior to 0.8.0 generated cache keys using only the URI path, excluding critical factors such as the host header. This allows an attacker to poison the cache and serve cross-origin responses to users.

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, or serve malicious content to legitimate users by poisoning shared cache entries.

Note: Cloudflare customers and Cloudflare's CDN infrastructure were 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.

### Patches We strongly suggest users should upgrade to Pingora v.0.8.0 or higher, which removes the default CacheKey implementation.

### Workarounds Do not rely on the provided CacheKey default, and at minimum use the host / :authority and the upstream peer TLS scheme as part of building the CacheKey, as well as other factors that may apply to the deployment e.g. HTTP method.

### References See [CVE-2026-2836](https://cve.org/CVERecord?id=CVE-2026-2836) and the [Cloudflare blog post](https://blog.cloudflare.com/pingora-oss-smuggling-vulnerabilities/) for more details.

### Credits Disclosed responsibly by Rajat Raghav (@xclow3n) through the Cloudflare [Bug Bounty Program](https://www.cloudflare.co…