RHSA-2026:38995HighCVSS 8.2

Red Hat Security Advisory: go-toolset:rhel8 security, bug fix, and enhancement update

Published
July 13, 2026
Last Modified
September 8, 2026

🔗 CVE IDs covered (6)

CVE-2026-39821 →CVE-2026-39822 →CVE-2026-42504 →CVE-2026-42505 →CVE-2026-42507 →CVE-2026-27145 →

📋 Description

CVE-2026-27145 — crypto/x509: golang: golang crypto/x509: Denial of Service via excessive processing of DNS SAN entries CVE-2026-39821 — golang.org/x/net/idna: golang: net/http: golang.org/x/net/idna: Privilege escalation via incorrect Punycode label processing CVE-2026-39822 — golang: Go os.Root: Symlink following vulnerability allows directory traversal CVE-2026-42504 — mime: golang: Golang MIME: Denial of Service via maliciously-crafted MIME header CVE-2026-42505 — crypto/tls: golang: Go crypto/tls: Information disclosure in Encrypted Client Hello CVE-2026-42507 — net/textproto: golang: Golang net/textproto: Misleading error messages via input injection

🎯 Affected products32

  • Red Hat Enterprise Linux AppStream (v. 8)
  • delve-0:1.26.1-1.module+el8.10.0+24516+40554724.aarch64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • delve-0:1.26.1-1.module+el8.10.0+24516+40554724.ppc64le (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • delve-0:1.26.1-1.module+el8.10.0+24516+40554724.src (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • delve-0:1.26.1-1.module+el8.10.0+24516+40554724.x86_64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • delve-debuginfo-0:1.26.1-1.module+el8.10.0+24516+40554724.aarch64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • delve-debuginfo-0:1.26.1-1.module+el8.10.0+24516+40554724.ppc64le (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • delve-debuginfo-0:1.26.1-1.module+el8.10.0+24516+40554724.x86_64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • delve-debugsource-0:1.26.1-1.module+el8.10.0+24516+40554724.aarch64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • delve-debugsource-0:1.26.1-1.module+el8.10.0+24516+40554724.ppc64le (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • delve-debugsource-0:1.26.1-1.module+el8.10.0+24516+40554724.x86_64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • go-toolset-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.aarch64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • go-toolset-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.ppc64le (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • go-toolset-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.s390x (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • go-toolset-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.x86_64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.aarch64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.ppc64le (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.s390x (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.src (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.x86_64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-bin-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.aarch64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-bin-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.ppc64le (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-bin-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.s390x (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-bin-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.x86_64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-docs-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.noarch (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-misc-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.noarch (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-race-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.aarch64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-race-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.ppc64le (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-race-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.s390x (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • golang-race-0:1.26.5-1.module+el8.10.0+24506+6809f2d9.x86_64 (go-toolset:rhel8) as a component of Red Hat Enterprise Linux AppStream (v. 8)
  • +2 more not shown

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 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: Upgrade to a fixed golang.org/x/net release that includes the idna correction, via updated golang or dependent package rebuilds. Workaround: There is no mitigation for this issue other than updating the Go toolchain to Go 1.25.12 or Go 1.26.5. Programs compiled with Go >= 1.24 that do not use the os.Root API are not affected by this vulnerability. The os.Root API was introduced in Go 1.24. Go versions prior to 1.24 are not affected. This issue is fixed in Go 1.25.12 and Go 1.26.5. 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. 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.

🔗 References (7)