CVE-2026-2833

An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.

Impact

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:

• Bypass proxy-level ACL controls and WAF logic

• Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests

• Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP

Cloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.

Mitigation:

Pingora users should upgrade to Pingora v0.8.0 or higher

As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.

An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.

Impact

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:

• Bypass proxy-level ACL controls and WAF logic

• Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests

• Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP

Cloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.

Mitigation:

Pingora users should upgrade to Pingora v0.8.0 or higher

As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-xq2h-p299-vjwv. This link is maintained to preserve external references.

Original Description

An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.

Impact

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:

• Bypass proxy-level ACL controls and WAF logic

• Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests

• Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP

Cloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.

Mitigation:

Pingora users should upgrade to Pingora v0.8.0 or higher

As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.

Impact

Pingora versions prior to 0.8.0 would immediately forward bytes following a request with an Upgrade header to the backend, without waiting for a 101 Switching Protocols response. This allows an attacker to smuggle requests to the backend and bypass proxy-level security controls.

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to bypass proxy-level ACL controls and WAF logic, poison caches and upstream connections, or perform cross-user attacks by hijacking sessions.

Note: Cloudflare customers and Cloudflare's CDN infrastructure were not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.

Patches

Pingora users should upgrade to Pingora v0.8.0 or higher, which fixes this issue by only switching connection modes after receiving a 101 Switching Protocols response from the backend (hash 824bdeefc61e121cc8861de1b35e8e8f39026ecd). Without a 101 response, subsequent bytes continue to be parsed as HTTP requests.

Workarounds

As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.

References

See CVE-2026-2833 and the Cloudflare blog post for more details.

Credits

Disclosed responsibly by Rajat Raghav (@xclow3n) through the Cloudflare Bug Bounty Program.

An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.

Impact

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:

• Bypass proxy-level ACL controls and WAF logic

• Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests

• Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP

Cloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.

Mitigation:

Pingora users should upgrade to Pingora v0.8.0 or higher

As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.

An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.

Impact

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:

• Bypass proxy-level ACL controls and WAF logic

• Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests

• Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP

Cloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.

Mitigation:

Pingora users should upgrade to Pingora v0.8.0 or higher

As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-xq2h-p299-vjwv. This link is maintained to preserve external references.

Original Description

An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.

Impact

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:

• Bypass proxy-level ACL controls and WAF logic

• Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests

• Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP

Cloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.

Mitigation:

Pingora users should upgrade to Pingora v0.8.0 or higher

As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.

Impact

Pingora versions prior to 0.8.0 would immediately forward bytes following a request with an Upgrade header to the backend, without waiting for a 101 Switching Protocols response. This allows an attacker to smuggle requests to the backend and bypass proxy-level security controls.

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to bypass proxy-level ACL controls and WAF logic, poison caches and upstream connections, or perform cross-user attacks by hijacking sessions.

Note: Cloudflare customers and Cloudflare's CDN infrastructure were not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.

Patches

Pingora users should upgrade to Pingora v0.8.0 or higher, which fixes this issue by only switching connection modes after receiving a 101 Switching Protocols response from the backend (hash 824bdeefc61e121cc8861de1b35e8e8f39026ecd). Without a 101 response, subsequent bytes continue to be parsed as HTTP requests.

Workarounds

As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.

References

See CVE-2026-2833 and the Cloudflare blog post for more details.

Credits

Disclosed responsibly by Rajat Raghav (@xclow3n) through the Cloudflare Bug Bounty Program.

Pingora versions prior to 0.8.0 would immediately forward bytes following a request with an Upgrade header to the backend, without waiting for a 101 Switching Protocols response. This allows an attacker to smuggle requests to the backend and bypass proxy-level security controls.

This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to bypass proxy-level ACL controls and WAF logic, poison caches and upstream connections, or perform cross-user attacks by hijacking sessions.

This flaw was corrected in commit 824bdeefc61e121cc8861de1b35e8e8f39026ecd by only switching connection modes after receiving a 101 response from the backend. Users should upgrade to Pingora >= 0.8.0.

Note: Cloudflare customers and Cloudflare's CDN infrastructure were not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.