Red Hat Security Advisory: yggdrasil security update

Fixed packages 5

Vulnerabilities 3

• Critical 9.6
  CVE-2026-39821

  Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna

  The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com") incorrectly returns the name "example.com" rather than an error. This behavior can lead to privilege …

  Go standard library golang.org/x/net net/http net/http/internal/http2 Debian Ubuntu Azure Linux Alpine Wolfi Go
  May 22, 2026
• High 7.5
  CVE-2026-33811

  Crash when handling long CNAME response in net

  When using LookupCNAME with the cgo DNS resolver, a very long CNAME response can trigger a double-free of C memory and a crash.

  Go standard library net golang go Debian Ubuntu Azure Linux Alpine Wolfi Go
  May 7, 2026
• Medium 6.5
  CVE-2026-27145 Public exploit

  Inefficient candidate hostname parsing in crypto/x509

  (*x509.Certificate).VerifyHostname previously called matchHostnames in a loop over all DNS Subject Alternative Name (SAN) entries. This caused strings.Split(host, ".") to execute repeatedly on the same input hostname. With a large DNS SAN list, verification c…

  Go standard library crypto/x509 golang stdlib Debian Ubuntu Azure Linux Wolfi Go
  Jun 2, 2026

References

• article
  https://access.redhat.com/security/updates/classification/#important
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2467822
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2480756
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2484207
• advisory
  https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_51187.json
• report
  https://access.redhat.com/security/cve/CVE-2026-27145
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-27145
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-27145
• article
  https://go.dev/cl/783621
• article
  https://go.dev/issue/79694
• article
  https://groups.google.com/g/golang-announce/c/tKs3rmcBcKw
• advisory
  https://pkg.go.dev/vuln/GO-2026-5037
• report
  https://access.redhat.com/security/cve/CVE-2026-33811
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-33811
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-33811
• article
  https://go.dev/cl/767860
• article
  https://go.dev/issue/78803
• article
  https://groups.google.com/g/golang-announce/c/qcCIEXso47M
• advisory
  https://pkg.go.dev/vuln/GO-2026-4981
• report
  https://access.redhat.com/security/cve/CVE-2026-39821
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-39821
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-39821
• article
  https://go.dev/cl/767220
• article
  https://go.dev/issue/78760
• article
  https://groups.google.com/g/golang-announce/c/iI-mYSI0lu8
• advisory
  https://pkg.go.dev/vuln/GO-2026-5026