ALAS2023-2026-1572

References: CVE-2026-25679  CVE-2026-27139  CVE-2026-27142  CVE-2026-33186 
FAQs regarding Amazon Linux ALAS/CVE Severity

Issue Overview:

url.Parse insufficiently validated the host/authority component and accepted some invalid URLs. (CVE-2026-25679)

On Unix platforms, when listing the contents of a directory using File.ReadDir or File.Readdir the returned FileInfo could reference a file outside of the Root in which the File was opened. The impact of this escape is limited to reading metadata provided by lstat from arbitrary locations on the filesystem without permitting reading or writing files outside the root. (CVE-2026-27139)

Actions which insert URLs into the content attribute of HTML meta tags are not escaped. This can allow XSS if the meta tag also has an http-equiv attribute with the value "refresh". A new GODEBUG setting has been added, htmlmetacontenturlescape, which can be used to disable escaping URLs in actions in the meta content attribute which follow "url=" by setting htmlmetacontenturlescape=0. (CVE-2026-27142)

gRPC-Go is the Go language implementation of gRPC. Versions prior to 1.79.3 have an authorization bypass resulting from improper input validation of the HTTP/2 `:path` pseudo-header. The gRPC-Go server was too lenient in its routing logic, accepting requests where the `:path` omitted the mandatory leading slash (e.g., `Service/Method` instead of `/Service/Method`). While the server successfully routed these requests to the correct handler, authorization interceptors (including the official `grpc/authz` package) evaluated the raw, non-canonical path string. Consequently, "deny" rules defined using canonical paths (starting with `/`) failed to match the incoming request, allowing it to bypass the policy if a fallback "allow" rule was present. This affects gRPC-Go servers that use path-based authorization interceptors, such as the official RBAC implementation in `google.golang.org/grpc/authz` or custom interceptors relying on `info.FullMethod` or `grpc.Method(ctx)`; AND that have a security policy contains specific "deny" rules for canonical paths but allows other requests by default (a fallback "allow" rule). The vulnerability is exploitable by an attacker who can send raw HTTP/2 frames with malformed `:path` headers directly to the gRPC server. The fix in version 1.79.3 ensures that any request with a `:path` that does not start with a leading slash is immediately rejected with a `codes.Unimplemented` error, preventing it from reaching authorization interceptors or handlers with a non-canonical path string. While upgrading is the most secure and recommended path, users can mitigate the vulnerability using one of the following methods: Use a validating interceptor (recommended mitigation); infrastructure-level normalization; and/or policy hardening. (CVE-2026-33186)

Issue Correction:
Run dnf update amazon-cloudwatch-agent --releasever 2023.11.20260413 or dnf update --advisory ALAS2023-2026-1572 --releasever 2023.11.20260413 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:
    amazon-cloudwatch-agent-1.300064.2-1.amzn2023.aarch64

src:
    amazon-cloudwatch-agent-1.300064.2-1.amzn2023.src

x86_64:
    amazon-cloudwatch-agent-1.300064.2-1.amzn2023.x86_64