Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip
The various Is methods (IsPrivate, IsLoopback, etc) did not work as expected for IPv4-mapped IPv6 addresses, returning false for addresses which would return true in their traditional IPv4 forms.
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
Errors returned from JSON marshaling may break template escaping in html/template
If errors returned from MarshalJSON methods contain user controlled data, they may be used to break the contextual auto-escaping behavior of the html/template package, allowing for subsequent actions to inject unexpected content into templates.
Comments in display names are incorrectly handled in net/mail
The ParseAddressList function incorrectly handles comments (text within parentheses) within display names. Since this is a misalignment with conforming address parsers, it can result in different trust decisions being made by programs using different parsers.
Incorrect forwarding of sensitive headers and cookies on HTTP redirect in net/http
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.
Memory exhaustion in multipart form parsing in net/textproto and net/http
When parsing a multipart form (either explicitly with Request.ParseMultipartForm or implicitly with Request.FormValue, Request.PostFormValue, or Request.FormFile), limits on the total size of the parsed form were not applied to the memory consumed while reading a single form line. This permits a maliciously crafted input containing very long lines to cause allocation of arbitrarily large amounts of memory, potentially leading to memory exhaustion. With fix, the ParseMultipartForm function now correctly limits the maximum size of form lines.
Verify panics on certificates with an unknown public key algorithm in crypto/x509
Verifying a certificate chain which contains a certificate with an unknown public key algorithm will cause Certificate.Verify to panic. This affects all crypto/tls clients, and servers that set Config.ClientAuth to VerifyClientCertIfGiven or RequireAndVerifyClientCert. The default behavior is for TLS servers to not verify client certificates.
Command 'go get' may unexpectedly fallback to insecure git in cmd/go
Using go get to fetch a module with the ".git" suffix may unexpectedly fallback to the insecure "git://" protocol if the module is unavailable via the secure "https://" and "git+ssh://" protocols, even if GOINSECURE is not set for said module. This only affects users who are not using the module proxy and are fetching modules directly (i.e. GOPROXY=off).
Denial of service via chunk extensions in net/http
A malicious HTTP sender can use chunk extensions to cause a receiver reading from a request or response body to read many more bytes from the network than are in the body. A malicious HTTP client can further exploit this to cause a server to automatically read a large amount of data (up to about 1GiB) when a handler fails to read the entire body of a request. Chunk extensions are a little-used HTTP feature which permit including additional metadata in a request or response body sent using the chunked encoding. The net/http chunked encoding reader discards this metadata. A sender can exploit this by inserting a large metadata segment with each
Before Go 1.20, the RSA based key exchange methods in crypto/tls may exhibit a timing side channel
Before Go 1.20, the RSA based TLS key exchanges used the math/big library, which is not constant time. RSA blinding was applied to prevent timing attacks, but analysis shows this may not have been fully effective. In particular it appears as if the removal of PKCS#1 padding may leak timing information, which in turn could be used to recover session key bits. In Go 1.20, the crypto/tls library switched to a fully constant time RSA implementation, which we do not believe exhibits any timing side channels.
Incorrect detection of reserved device names on Windows in path/filepath
On Windows, The IsLocal function does not correctly detect reserved device names in some cases. Reserved names followed by spaces, such as "COM1 ", and reserved names "COM" and "LPT" followed by superscript 1, 2, or 3, are incorrectly reported as local. With fix, IsLocal now correctly reports these names as non-local.
Insecure parsing of Windows paths with a \??\ prefix in path/filepath
The filepath package does not recognize paths with a \??\ prefix as special. On Windows, a path beginning with \??\ is a Root Local Device path equivalent to a path beginning with \\?\. Paths with a \??\ prefix may be used to access arbitrary locations on the system. For example, the path \??\c:\x is equivalent to the more common path c:\x. Before fix, Clean could convert a rooted path such as \a\..\??\b into the root local device path \??\b. Clean will now convert this to .\??\b. Similarly, Join(\, ??, b) could convert a seemingly innocent sequence of path elements into the root local device path \??\b. Join will now convert this to \.\??\b.
HTTP/2 rapid reset can cause excessive work in net/http
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 un
Arbitrary code execution during build via line directives in cmd/go
Line directives ("//line") can be used to bypass the restrictions on "//go:cgo_" directives, allowing blocked linker and compiler flags to be passed during compilation. This can result in unexpected execution of arbitrary code when running "go build". The line directive requires the absolute path of the file in which the directive lives, which makes exploiting this issue significantly more complex.
Improper handling of special tags within script contexts in html/template
The html/template package does not apply the proper rules for handling occurrences of "<script", "<!--", and "</script" within JS literals in <script> contexts. This may cause the template parser to improperly consider script contexts to be terminated early, causing actions to be improperly escaped. This could be leveraged to perform an XSS attack.
Improper handling of HTML-like comments in script contexts in html/template
The html/template package does not properly handle HTML-like "" comment tokens, nor hashbang "#!" comment tokens, in <script> contexts. This may cause the template parser to improperly interpret the contents of <script> contexts, causing actions to be improperly escaped. This may be leveraged to perform an XSS attack.
Large RSA keys can cause high CPU usage in crypto/tls
Extremely large RSA keys in certificate chains can cause a client/server to expend significant CPU time verifying signatures. With fix, the size of RSA keys transmitted during handshakes is restricted to <= 8192 bits. Based on a survey of publicly trusted RSA keys, there are currently only three certificates in circulation with keys larger than this, and all three appear to be test certificates that are not actively deployed. It is possible there are larger keys in use in private PKIs, but we target the web PKI, so causing breakage here in the interests of increasing the default safety of users of crypto/tls seems reasonable.
Insufficient sanitization of Host header in net/http
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.
Improper sanitization of LDFLAGS with embedded spaces in go command with cgo in cmd/go
The go command may execute arbitrary code at build time when using cgo. This may occur when running "go get" on a malicious module, or when running any other command which builds untrusted code. This is can by triggered by linker flags, specified via a "#cgo LDFLAGS" directive. Flags containing embedded spaces are mishandled, allowing disallowed flags to be smuggled through the LDFLAGS sanitization by including them in the argument of another flag. This only affects usage of the gccgo compiler.
Improper handling of non-optional LDFLAGS in go command with cgo in cmd/go
The go command may execute arbitrary code at build time when using cgo. This may occur when running "go get" on a malicious module, or when running any other command which builds untrusted code. This is can by triggered by linker flags, specified via a "#cgo LDFLAGS" directive. The arguments for a number of flags which are non-optional are incorrectly considered optional, allowing disallowed flags to be smuggled through the LDFLAGS sanitization. This affects usage of both the gc and gccgo compilers.