MGASA-2026-0341

CVE-2026-56865 A malicious GOPROXY was previously capable of forging up to two sumdb tiles that allow for a requested module to bypass the GOSUMDB check and persist attacker-controlled module content to a local Go module cache. CVE-2026-56864 A malicious GOSUMDB was capable of serving arbitrary module content not contained within the transparency log. CVE-2026-56859 Previously, DecodeElement would reset the depth counter causing it to never fire; this could lead to stack exhaustion. CVE-2026-56853 When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. Previously, this was being done with no timeout applied. ReadHeaderTimeout is now applied for this. CVE-2026-56860 Previously, resolving relative paths containing parent directory (|..|) segments performed string conversions and buffer rewrites on each step, resulting in quadratic time complexity and high memory allocation overhead. CVE-2026-4660 Parsing an invalid SVCB or HTTPS RR can panic when the size of a parameter value overflows the message buffer. CVE-2026-56862 Previously, we always counted handshake messages, such as KeyUpdate, as state-advancing, regardless of whether a handshake has been completed or not. As a result, a malicious client can keep sending KeyUpdate messages to force the server to keep performing key derivation operations indefinitely. CVE-2026-56858 Previously, pathological inputs could close an unescaped |/| early, allowing for attack-controlled data to inject arbitrary content, potentially leading to XSS. CVE-2026-39821 The ToASCII and ToUnicode functions incorrectly accepted Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com") incorrectly returned the name "example.com" rather than an error. CVE-2026-33818 Enforce a recursion limit in Unmarshal to prevent stack exhaustion when parsing deeply-nested, recursive structures.