CVE-2026-63374
Description
A flaw was found in AnyIO. A remote attacker in a privileged network position can bypass Transport Layer Security (TLS) certificate validation when connecting to internationalized domain names. This vulnerability occurs because the framework converts internationalized hostnames using an outdated encoding standard, Internationalizing Domain Names in Applications (IDNA) 2003 instead of IDNA 2008. If network traffic is redirected or intercepted, an attacker can present a legitimate certificate for the mismatched domain name, allowing them to impersonate the intended server and intercept or alter sensitive communications.
Statement
This vulnerability is rated as having a Moderate severity for Red Hat products because exploitation requires an attacker to already be positioned to intercept network traffic, and the flaw only manifests when connecting to internationalized domain names containing non-ASCII characters. Within Red Hat supported environments and containerized AI components, workloads predominantly communicate using standard ASCII fully qualified domain names and internal endpoints. Because the defect does not allow remote code execution and requires a prior man-in-the-middle condition, the overall blast radius is constrained to specific redirected sessions.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.4 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | High | N/A | N/A |
| Privileges Required | None | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | High | N/A | N/A |
| Integrity Impact | High | N/A | N/A |
| Availability Impact | None | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Red Hat CVSS v3 Score Explanation
Manually derived (not AEGIS/tool-generated): AC:H reflects the CVSS v3.1 spec's own canonical High-complexity example (attacker must inject into the logical network path / MITM) since exploitation requires the connection to already be hijacked/redirected via other means before the IDNA2003-vs-2008 cert-validation bug becomes exploitable; C:H/I:H/A:N mirrors CVEORG's own v4 impact split (VC:H/VI:H/VA:N). Score cross-checked against RH severity classification criteria (access.redhat.com/security/updates/classification): no arbitrary-code-execution/system-compromise, and a real MITM precondition plus IDN-hostname-only scope -> Moderate impact, not Critical.
Understanding the Weakness (CWE)
Integrity,Authentication
Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity
When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The product might connect to a malicious host while believing it is a trusted host, or the product might be deceived into accepting spoofed data that appears to originate from a trusted host.
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