Red Hat Security Advisory: golang security, bug fix, and enhancement update

Fixed packages 8

Vulnerabilities 15

• Critical 9.1
  CVE-2026-78663

  Double flow control refund on HTTP/2 server streams in net/http

  The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client…

  Go standard library golang.org/x/net net/http golang.org/x/net/http2 Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.8
  CVE-2026-94444

  Checksum bypass for golang.org/fips140 in cmd/go

  Previously, a user operating inside of a malicious Go project that defines a bogus golang.org/fips140 and operates a malicious GOMODPROXY the user chooses to connect to can serve an arbitrary module in its place. We now unpack the trusted ziphash for the bund…

  Go toolchain cmd/go golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.8
  CVE-2026-94447

  Checksum database bypass for golang.org/toolchain in cmd/go

  Previously, a user operating inside of a malicious Go project that defines a bogus golang.org/toolchain go.sum entry and operates a malicious GOMODPROXY the user chooses to use can bypass the intended checksum. We now ensure that golang.org/toolchain always g…

  Go toolchain cmd/go golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-56866

  HTTP/1 client connection desynchronization after CONNECT rejection in net/http

  When http.Transport sends an HTTP/1 CONNECT request with a non-empty Request.Body, it writes the body directly to the connection without framing after the request headers. If the server rejects the CONNECT request with a non-2xx keep-alive response, Transport…

  Go standard library net/http net/http/httputil golang Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-78659

  HTTP/2 server memory exhaustion due to Trailer headers in net/http

  When "Trailer" headers are sent by a client, the HTTP server internally uses the header values to populate the Request.Trailer map passed to the server handler. Because Request.Trailer is a map, each entry incurs memory overhead. For HTTP/2 servers, a malicio…

  Go standard library golang.org/x/net net/http golang.org/x/net/http2 Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-78660

  HTTP/2 transport accepts malformed framing-related headers in net/http

  Historically, we have been rather lax about malformed framing-related headers in our HTTP/2 implementation, as they cannot interfere with HTTP/2 framing. However, this makes it possible for our HTTP/2 implementation to forward responses containing such header…

  Go standard library golang.org/x/net net/http golang.org/x/net/http2 Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-78667

  Lack of limit on size of parsed Range headers in net/http

  When parsing a Range header containing a large number of small ranges, FileServer(FS), ServeContent, and ServeFile(FS) can consume an excessive amount of CPU.

  Go standard library net/http golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-78669

  Excessive CPU consumption from repeated initial window changes in net/http

  A malicious HTTP/2 peer can cause excessive CPU consumption in the client or server by opening a large number of streams and then sending many small SETTINGS frames containing SETTINGS_INITIAL_WINDOW_SIZE values.

  Go standard library golang.org/x/net net/http golang.org/x/net/http2 Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-94439

  HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http

  When an HTTP server handler sends a 2xx response to an HTTP/1 CONNECT request and returns without hijacking the connection, the server improperly continues to read and serve requests from the connection. Since a 2xx response to an HTTP/1 CONNECT converts the …

  Go standard library net/http golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-94440

  Memory limit bypass when parsing MIME headers in net/textproto, mime/multipart

  Parsing a multipart form can bypass memory limits and read an arbitrarily long line into memory when the remaining limit at the start of a part is less than 400 bytes.

  Go standard library net/textproto mime/multipart golang Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-97031

  Reject malformed ECH outer extension references in crypto/tls

  Multiple ECH outer extension references are not permitted under RFC 9849; previously, a client could send a well-crafted packet that could trigger memory exhaustion in the server process by specifying multiple references. We now reject these as malformed and …

  Go standard library crypto/tls golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• High 7.5
  CVE-2026-97032

  HTTP/2 server crash due to HPACK encoder race in net/http

  HTTP/2 servers could end up crashing due to inadvertently modifying its HPACK encoder concurrently. This happens because the server modifies the HPACK encoder from two goroutines without synchronization: one uses the encoder to encode a HEADERS frame as part …

  Go standard library golang.org/x/net net/http golang.org/x/net/http2 Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• Medium 6.8
  CVE-2026-111943 Public exploit

  Distrust compromised intermediate certificates in crypto/x509

  On most platforms, Go uses the given system root certificates. However, in some narrower cases, the system trust stores may not be updated without further action. To defend against the narrower set of cases that may remain affected, a denylist was added in cr…

  Go standard library crypto/x509 golang go Debian Ubuntu Azure Linux Alpine Wolfi Go crates.io
  Oct 21, 2026
• Medium 6.1
  CVE-2026-94448

  Reset context tracking on consecutive template expressions in html/template

  When a JavaScript template literal contains consecutive expressions, the context tracking state was not properly reset upon entering a new expression. We now ensure that template-literal expression entries correctly reset context variables so all subsequent r…

  Go standard library html/template golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026
• Medium 6.1
  CVE-2026-97030

  Recognize yield as regexp preceder keyword in html/template

  A trusted template author may have previously written a valid template wherein the use of the 'yield' keyword would not be correctly escaped. We now ensure that valid keyword uses are escaped and non-keyword uses are not escaped.

  Go standard library html/template golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  Oct 8, 2026

References

• article
  https://access.redhat.com/security/updates/classification/#important
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548334
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548336
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548344
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2556068
• article
  https://issues.redhat.com/browse/RHEL-287192
• advisory
  https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_86196.json
• report
  https://access.redhat.com/security/cve/CVE-2026-56866
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548347
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-56866
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-56866
• article
  https://go.dev/cl/847306
• article
  https://go.dev/issue/81740
• article
  https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
• advisory
  https://pkg.go.dev/vuln/GO-2026-6605
• report
  https://access.redhat.com/security/cve/CVE-2026-78659
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548339
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-78659
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-78659
• article
  https://go.dev/cl/847185
• article
  https://go.dev/cl/847314
• article
  https://go.dev/issue/81857
• article
  https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs
• advisory
  https://pkg.go.dev/vuln/GO-2026-6603
• report
  https://access.redhat.com/security/cve/CVE-2026-78660
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548340
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-78660
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-78660
• article
  https://go.dev/cl/835145
• article
  https://go.dev/cl/836385
• article
  https://go.dev/issue/81115
• advisory
  https://pkg.go.dev/vuln/GO-2026-6610
• report
  https://access.redhat.com/security/cve/CVE-2026-78663
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2548345
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-78663
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-78663
• article
  https://go.dev/cl/847187
• article
  https://go.dev/cl/847310
• article
  https://go.dev/issue/81743