CVE-2026-105299: Pingora forwards client-nominated Connection headers to HTTP/1 upstreams, allowing ACL bypass in specific chained deployments
Summary
Before version 0.9.0, the HTTP/1 upstream path in pingora-proxy passed the downstream request through upstreamrequestfilter and wrote it to the upstream without removing the client's Connection header, other hop-by-hop headers, or the headers Connection nominated, although RFC 9110 Section 7.6.1 requires intermediaries to remove them. The HTTP/2 upstream path already removed Connection and related HTTP/1-specific headers. A client could therefore nominate a header that the application adds in upstreamrequestfilter (for example, Connection: keep-alive, X-Forwarded-For). A downstream HTTP/1 intermediary that honors Connection would then strip the Pingora-added header before it reached the origin.
Impact
Specifically affects chained deployments where an HTTP/1 intermediary between Pingora and the origin processes Connection nominations (for example, Go's net/http/httputil.ReverseProxy) and the origin trusts headers added by that intermediary (for example, X-Forwarded-For for IP-based authorization). A remote, unauthenticated attacker can have those headers removed, potentially bypassing authorization. The reporter demonstrated access to an IP-restricted endpoint using X-Forwarded-For for IP validation on the origin. This is the same class of issue as CVE-2022-31813 in Apache HTTP Server.
Note that Cloudflare CDN customers were unaffected, as no such chained deployment as described above exists with internal Pingora services, and Connection headers are sanitized before arriving at Pingora gateways.
Mitigation:
Upgrade to pingora 0.9.0 or later. By default, Pingora now removes hop-by-hop and Connection-nominated headers from upstream requests, and rejects requests whose Connection header nominates Host, X-Forwarded-For, X-Forwarded-Host, X-Forwarded-Proto, or a pseudo-header. This is controlled by PeerOptions::httpupstreamrequestpolicy (HttpUpstreamRequestPolicy). Fix commits: https://github.com/cloudflare/pingora/commit/28c18e6b6b04dd0bd937234e5950049e6d74cded , https://github.com/cloudflare/pingora/commit/ca23f1668eca8e78be7ba62ef0edbd458b40eeee
Do not use HttpUpstreamRequestPolicy::preserve() if the origin relies on headers added by Pingora; it restores the old passthrough behavior.
If you cannot upgrade: in upstreamrequestfilter, remove the Connection header and every header it nominates before adding trusted headers.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pingorato a version that resolves this vulnerability.Fixed in 0.9.0 - Configuration
Do not configure HttpUpstreamRequestPolicy::preserve(), because it restores the old passthrough behavior and can forward client-nominated headers.
Pingora PeerOptions::http_upstream_request_policy = do not use HttpUpstreamRequestPolicy::preserve() - Compensating control
In upstream_request_filter, remove the Connection header and every header it nominates before adding trusted headers.
Event History
Frequently Asked Questions
Which deployments are realistically exposed?
Exposure requires Pingora to use an HTTP/1 upstream path, with another HTTP/1 intermediary between Pingora and the origin that honors Connection header nominations. The origin must also trust a header added by that intermediary, such as X-Forwarded-For, for a security decision like IP-based authorization.
What does an attacker need to exploit this?
The attacker can be remote and unauthenticated. They need to send a client Connection header that nominates a security-relevant header added during Pingora's upstream_request_filter processing, causing a downstream HTTP/1 intermediary to remove that header before forwarding to the origin.
Are HTTP/2 upstream connections affected?
No. The HTTP/2 upstream path already removes Connection and related HTTP/1-specific headers.
How can I determine whether my deployment is affected?
Check whether Pingora forwards requests to an HTTP/1 intermediary before the origin, whether that intermediary processes Connection nominations, and whether the origin relies on intermediary-added headers for authorization. Affected behavior is present before version 0.9.0.