Pingora forwards client-nominated Connection headers to HTTP/1 upstreams, allowing ACL bypass in specific chained deployments

Pingora versions prior to 0.9.0 passed the downstream request through `upstream_request_filter` and wrote it to HTTP/1 upstreams 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 `upstream_request_filter` (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. This 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. This is the same class of issue as CVE-2022-31813 in Apache HTTP Server. This flaw was corrected in commits 28c18e6b6b04dd0bd937234e5950049e6d74cded and ca23f1668eca8e78be7ba62ef0edbd458b40eeee. 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::http_upstream_request_policy`; `HttpUpstreamRequestPolicy::preserve()` restores the old passthrough behavior and should not be used if the origin relies on headers added by Pingora. Users should upgrade to Pingora >= 0.9.0. Note: 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.

Source published

20 Oct 2026 12:00:00 UTC

Source modified

26 Oct 2026 11:15:11 UTC

Observed here

26 Oct 2026 11:36:11 UTC

Source terms

OSV · upstream source license applies

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CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N