Cloudflare pingora up to 0.8.0 HTTP/2 Server default_h2_options max_header_list_size/max_concurrent_streams allocation of resources

Summaryinfo

A vulnerability described as problematic has been identified in Cloudflare pingora up to 0.8.0. Affected by this issue is the function pingora_core::protocols::http::v2::server::default_h2_options of the component HTTP2 Server. Such manipulation of the argument max_header_list_size/max_concurrent_streams leads to allocation of resources. This vulnerability is listed as CVE-2026-105297. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Cloudflare pingora up to 0.8.0. Affected by this issue is the function pingora_core::protocols::http::v2::server::default_h2_options of the component HTTP2 Server. The manipulation of the argument max_header_list_size/max_concurrent_streams with an unknown input leads to a allocation of resources vulnerability. Using CWE to declare the problem leads to CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. Impacted is availability. CVE summarizes:

Summary Before version 0.8.1, Pingora's HTTP/2 server used the h2 crate's default limits unless the application set its own 16 MiB decoded header-list size and no limit on concurrent streams. A remote, unauthenticated client can send 1-byte HPACK references to a near-empty header, making the server allocate hundreds of thousands of header fields per stream across an unlimited number of streams on one connection, and use HTTP/2 flow control to keep those streams open. This can exhaust memory and degrade or terminate the Pingora process. Impact Remote, unauthenticated denial of service against any Pingora service that terminates HTTP/2 (h2 or h2c) without explicitly setting max_header_list_size and max_concurrent_streams. The reporter showed that a single connection could get a Pingora process with a 2 GiB memory limit OOM-killed. Note that Cloudflare CDN customers were unaffected, as internal Pingora services at Cloudflare do not have HTTP/2 clients. Mitigation: * Upgrade to pingora 0.8.1 or later (fix: https://github.com/cloudflare/pingora/commit/d193c8d49b8b7c1c1ede93183759caa4f6906bbd ). When no H2Options are supplied, Pingora now advertises and enforces a 64 KiB decoded header-list limit and at most 100 concurrent streams per connection. * Applications that supply their own H2Options are not covered by these defaults and must set max_header_list_size and max_concurrent_streams explicitly (this also works on versions before 0.8.1), or, on 0.8.1 and later, start from pingora_core::protocols::http::v2::server::default_h2_options(). H2Options::default() does not include these limits.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-105297 since 10/05/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 0.8.1 eliminates this vulnerability. Applying the patch d193c8d49b8b7c1c1ede93183759caa4f6906bbd is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Cloud Software

Vendor

• Cloudflare

Name

• pingora

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8.0

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CPE 2.2info

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