ALAS2023-2026-1876

References: CVE-2026-27145  CVE-2026-42504  CVE-2026-42507 
FAQs regarding Amazon Linux ALAS/CVE Severity

Issue Overview:

(*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 costs scaled quadratically based on the number of SAN entries multiplied by the hostname's label count. Because x509.Verify validates hostnames before building the certificate chain, this overhead occurred even for untrusted certificates. (CVE-2026-27145)

Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU. (CVE-2026-42504)

When returning errors, functions in the net/textproto package would include its input as part of the error. This might allow an attacker to inject misleading content to errors that are printed or logged. (CVE-2026-42507)

Issue Correction:
Run dnf update golang-github-burntsushi-toml-test --releasever 2023.12.20260622 or dnf update --advisory ALAS2023-2026-1876 --releasever 2023.12.20260622 to update your system.
More information on how to update your system can be found on this page: Amazon Linux 2023 documentation

New Packages:

aarch64:
    golang-github-burntsushi-toml-test-debuginfo-0.2.0-8.amzn2023.0.4.aarch64
    golang-github-burntsushi-toml-test-debugsource-0.2.0-8.amzn2023.0.4.aarch64
    golang-github-burntsushi-toml-test-0.2.0-8.amzn2023.0.4.aarch64

noarch:
    golang-github-burntsushi-toml-test-devel-0.2.0-8.amzn2023.0.4.noarch

src:
    golang-github-burntsushi-toml-test-0.2.0-8.amzn2023.0.4.src

x86_64:
    golang-github-burntsushi-toml-test-debuginfo-0.2.0-8.amzn2023.0.4.x86_64
    golang-github-burntsushi-toml-test-debugsource-0.2.0-8.amzn2023.0.4.x86_64
    golang-github-burntsushi-toml-test-0.2.0-8.amzn2023.0.4.x86_64