RHSA-2026:23264HighCVSS 8.2

Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

Published
June 4, 2026
Last Modified
August 26, 2026

🔗 CVE IDs covered (14)

CVE-2026-39821 →CVE-2026-39825 →CVE-2026-39826 →CVE-2026-42501 →CVE-2026-42504 →CVE-2026-33811 →CVE-2026-33814 →CVE-2026-39823 →CVE-2026-39836 →CVE-2026-42507 →CVE-2026-42508 →CVE-2026-46595 →CVE-2026-27145 →CVE-2026-39820 →

📋 Description

CVE-2026-27145 — crypto/x509: golang: golang crypto/x509: Denial of Service via excessive processing of DNS SAN entries CVE-2026-33811 — net: golang: Go net package: Denial of Service via long CNAME response in LookupCNAME CVE-2026-33814 — net/http/internal/http2: golang: golang.org/x/net: Go HTTP/2: Denial of Service via malformed SETTINGS_MAX_FRAME_SIZE frame CVE-2026-39820 — net/mail: golang: Go net/mail: Denial of Service via crafted email inputs CVE-2026-39821 — golang.org/x/net/idna: golang: net/http: golang.org/x/net/idna: Privilege escalation via incorrect Punycode label processing CVE-2026-39823 — html/template: golang: Go html/template: Cross-Site Scripting via improper URL escaping in meta tag content CVE-2026-39825 — net/http/httputil: golang: net/http/httputil: ReverseProxy forwards hidden query parameters, potentially bypassing security controls CVE-2026-39826 — html/template: golang: html/template: Cross-site scripting due to incorrect script tag escaping CVE-2026-39836 — net: golang: Go net package: Denial of Service via NUL byte in Dial and LookupPort on Windows CVE-2026-42501 — cmd/go: golang: Go command (cmd/go): Integrity bypass due to checksum validation flaw via malicious module proxy CVE-2026-42504 — mime: golang: Golang MIME: Denial of Service via maliciously-crafted MIME header CVE-2026-42507 — net/textproto: golang: Golang net/textproto: Misleading error messages via input injection CVE-2026-42508 — golang.org/x/crypto/ssh/knownhosts: golang: golang.org/x/crypto/ssh/knownhosts: Revocation bypass via unchecked SignatureKey CVE-2026-46595 — golang.org/x/crypto/ssh: golang.org/x/crypto/ssh: Authorization bypass due to skipped source-address validation

🎯 Affected products5

  • Red Hat Hardened Images
  • golang1-26-main@aarch64 as a component of Red Hat Hardened Images
  • golang1-26-main@noarch as a component of Red Hat Hardened Images
  • golang1-26-main@src as a component of Red Hat Hardened Images
  • golang1-26-main@x86_64 as a component of Red Hat Hardened Images

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/ Workaround: A flaw was found in the Go standard library crypto/x509 package. When verifying a TLS certificate hostname, VerifyHostname processed each DNS Subject Alternative Name (SAN) entry in a loop and repeatedly split the candidate hostname on "." characters. For certificates with a very large DNS SAN list, CPU use could grow quadratically with the number of SAN entries and hostname labels. Because hostname verification runs before the certificate chain is built, this overhead can occur even when the certificate is not trusted. Red Hat rates this issue as Important. It affects Red Hat products that include the Go standard library crypto/x509 code from an affected Go toolchain version (before Go 1.25.11, or from Go 1.26.0 through Go 1.26.3). Applications and container images built with a fixed Go release (1.25.11 or later, or 1.26.4 or later) are not affected. Community distributions such as Fedora are also affected. Upstream fix: Go 1.25.11 and Go 1.26.4 (GO-2026-5037). Workaround: To mitigate this issue, applications can be configured to use the pure Go DNS resolver instead of the `cgo` DNS resolver. This can be achieved by setting the `GODEBUG` environment variable to `netdns=go`. For example, to run a Go application with this mitigation: `GODEBUG=netdns=go /path/to/your/go/application`. This change may require restarting affected applications or services to take effect. Users should verify that this change does not negatively impact DNS resolution for their specific application environment. Workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Workaround: Upgrade to a fixed golang.org/x/net release that includes the idna correction, via updated golang or dependent package rebuilds. Workaround: Ensure that user-supplied URLs are validated and sanitized before being passed to Go's `html/template` package for rendering in HTML meta tag content attributes. Avoid rendering untrusted URL data directly in meta tag content attributes. Workaround: Increase the maximum number of query parameters allowed by setting the GODEBUG environment variable `urlmaxqueryparams` to a higher value (e.g., `GODEBUG=urlmaxqueryparams=20000`), or validate and enforce security controls on query parameters at the backend service rather than relying solely on the ReverseProxy's Rewrite or Director function for security filtering. Workaround: To verify the integrity of Go module dependencies and detect potential tampering by a malicious proxy, users can revalidate all dependencies of the current module. This process involves removing the existing `go.sum` file and then re-generating and verifying module checksums. Execute the following commands in your module's root directory: ```bash rm go.sum go mod tidy go mod verify ``` This operation will re-download and re-verify all module dependencies. Be aware that this may affect your local module cache and could require re-building projects. Workaround: To mitigate this issue, restrict network access to services that process MIME headers from untrusted sources. Implement input validation and sanitization for all incoming data, especially MIME headers, to prevent maliciously crafted content from being processed by applications utilizing the vulnerable Golang MIME package.

🔗 References (18)