Net/Http

When processing HTTP/2 SETTINGS frames, transport will enter an infinite loop of writing CONTINUATION frames if it receives a SETTINGS_MAX_FRAME_SIZE with a value of 0.

Published: 2026-05-07T19:41:17.631Z
Updated: 2026-05-08T18:01:02.989Z

Despite HTTP headers having a default limit of 1MB, the number of cookies that can be parsed does not have a limit. By sending a lot of very small cookies such as "a=;", an attacker can make an HTTP server allocate a large amount of structs, causing large memory consumption.

Published: 2025-10-29T22:10:13.912Z
Updated: 2025-11-04T21:13:35.468Z

Proxy-Authorization and Proxy-Authenticate headers persisted on cross-origin redirects potentially leaking sensitive information.

Published: 2025-06-11T16:42:53.054Z
Updated: 2025-06-11T17:59:48.033Z

When using http.CrossOriginProtection, the AddInsecureBypassPattern method can unexpectedly bypass more requests than intended. CrossOriginProtection then skips validation, but forwards the original request path, which may be served by a different handler without the intended security protections.

Published: 2025-09-22T21:01:55.440Z
Updated: 2025-09-24T13:29:45.405Z

Matching of hosts against proxy patterns can improperly treat an IPv6 zone ID as a hostname component. For example, when the NO_PROXY environment variable is set to "*.example.com", a request to "[::1%25.example.com]:80` will incorrectly match and not be proxied.

Published: 2025-03-12T18:27:59.376Z
Updated: 2026-04-16T22:39:33.619Z

The HTTP client drops sensitive headers after following a cross-domain redirect. For example, a request to a.com/ containing an Authorization header which is redirected to b.com/ will not send that header to b.com. In the event that the client received a subsequent same-domain redirect, however, the sensitive headers would be restored. For example, a chain of redirects from a.com/, to b.com/1, and finally to b.com/2 would incorrectly send the Authorization header to b.com/2.

Published: 2025-01-28T01:03:24.869Z
Updated: 2025-09-18T18:41:11.116Z

The net/http HTTP/1.1 client mishandled the case where a server responds to a request with an "Expect: 100-continue" header with a non-informational (200 or higher) status. This mishandling could leave a client connection in an invalid state, where the next request sent on the connection will fail. An attacker sending a request to a net/http/httputil.ReverseProxy proxy can exploit this mishandling to cause a denial of service by sending "Expect: 100-continue" requests which elicit a non-informational response from the backend. Each such request leaves the proxy with an invalid connection, and causes one subsequent request using that connection to fail.

Published: 2024-07-02T21:28:25.677Z
Updated: 2024-10-04T15:02:46.565Z

When following an HTTP redirect to a domain which is not a subdomain match or exact match of the initial domain, an http.Client does not forward sensitive headers such as "Authorization" or "Cookie". For example, a redirect from foo.com to www.foo.com will forward the Authorization header, but a redirect to bar.com will not. A maliciously crafted HTTP redirect could cause sensitive headers to be unexpectedly forwarded.

Published: 2024-03-05T22:22:30.306Z
Updated: 2025-02-13T17:14:01.755Z

An attacker may cause an HTTP/2 endpoint to read arbitrary amounts of header data by sending an excessive number of CONTINUATION frames. Maintaining HPACK state requires parsing and processing all HEADERS and CONTINUATION frames on a connection. When a request's headers exceed MaxHeaderBytes, no memory is allocated to store the excess headers, but they are still parsed. This permits an attacker to cause an HTTP/2 endpoint to read arbitrary amounts of header data, all associated with a request which is going to be rejected. These headers can include Huffman-encoded data which is significantly more expensive for the receiver to decode than for an attacker to send. The fix sets a limit on the amount of excess header frames we will process before closing a connection.

Published: 2024-04-04T20:37:30.714Z
Updated: 2025-11-04T18:17:43.583Z

A malicious HTTP/2 client which rapidly creates requests and immediately resets them can cause excessive server resource consumption. While the total number of requests is bounded by the http2.Server.MaxConcurrentStreams setting, resetting an in-progress request allows the attacker to create a new request while the existing one is still executing. With the fix applied, HTTP/2 servers now bound the number of simultaneously executing handler goroutines to the stream concurrency limit (MaxConcurrentStreams). New requests arriving when at the limit (which can only happen after the client has reset an existing, in-flight request) will be queued until a handler exits. If the request queue grows too large, the server will terminate the connection. This issue is also fixed in golang.org/x/net/http2 for users manually configuring HTTP/2. The default stream concurrency limit is 250 streams (requests) per HTTP/2 connection. This value may be adjusted using the golang.org/x/net/http2 package; see the Server.MaxConcurrentStreams setting and the ConfigureServer function.

Published: 2023-10-11T21:15:02.727Z
Updated: 2025-02-13T17:02:50.341Z

The HTTP/1 client does not fully validate the contents of the Host header. A maliciously crafted Host header can inject additional headers or entire requests. With fix, the HTTP/1 client now refuses to send requests containing an invalid Request.Host or Request.URL.Host value.

Published: 2023-07-11T19:23:58.511Z
Updated: 2025-02-13T16:49:14.579Z

A maliciously crafted HTTP/2 stream could cause excessive CPU consumption in the HPACK decoder, sufficient to cause a denial of service from a small number of small requests.

Published: 2023-02-28T17:19:45.801Z
Updated: 2025-05-05T16:12:28.159Z

On Windows, restricted files can be accessed via os.DirFS and http.Dir. The os.DirFS function and http.Dir type provide access to a tree of files rooted at a given directory. These functions permit access to Windows device files under that root. For example, os.DirFS("C:/tmp").Open("COM1") opens the COM1 device. Both os.DirFS and http.Dir only provide read-only filesystem access. In addition, on Windows, an os.DirFS for the directory (the root of the current drive) can permit a maliciously crafted path to escape from the drive and access any path on the system. With fix applied, the behavior of os.DirFS("") has changed. Previously, an empty root was treated equivalently to "/", so os.DirFS("").Open("tmp") would open the path "/tmp". This now returns an error.

Published: 2022-12-07T16:11:18.867Z
Updated: 2025-04-23T15:43:46.208Z

An attacker can cause excessive memory growth in a Go server accepting HTTP/2 requests. HTTP/2 server connections contain a cache of HTTP header keys sent by the client. While the total number of entries in this cache is capped, an attacker sending very large keys can cause the server to allocate approximately 64 MiB per open connection.

Published: 2022-12-08T19:03:53.161Z
Updated: 2025-02-13T16:33:08.284Z

Improper exposure of client IP addresses in net/http before Go 1.17.12 and Go 1.18.4 can be triggered by calling httputil.ReverseProxy.ServeHTTP with a Request.Header map containing a nil value for the X-Forwarded-For header, which causes ReverseProxy to set the client IP as the value of the X-Forwarded-For header.

Published: 2022-08-09T20:18:21.000Z
Updated: 2026-03-06T19:06:52.828Z

Acceptance of some invalid Transfer-Encoding headers in the HTTP/1 client in net/http before Go 1.17.12 and Go 1.18.4 allows HTTP request smuggling if combined with an intermediate server that also improperly fails to reject the header as invalid.

Published: 2022-08-09T20:16:57.000Z
Updated: 2026-03-06T17:46:56.094Z