CVE-2025-21355
Published: 19 February 2025
Summary
CVE-2025-21355 is a high-severity Missing Authentication for Critical Function (CWE-306) vulnerability in Microsoft Bing. Its CVSS base score is 8.6 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 8.5% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 AC-14 (Permitted Actions Without Identification or Authentication) and IA-8 (Identification and Authentication (Non-organizational Users)).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly addresses missing authentication for critical functions by explicitly identifying and limiting permitted actions without identification or authentication.
Requires unique identification and authentication for non-organizational users, preventing unauthorized network access to critical functions in public-facing services like Microsoft Bing.
Mandates timely identification, reporting, and correction of flaws such as this missing authentication vulnerability through testing and patching.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability is a missing authentication for a critical function in the public-facing Microsoft Bing service, directly enabling unauthenticated remote code execution over the network with no privileges or user interaction required, which maps to exploitation of public-facing applications.
NVD Description
Missing Authentication for Critical Function in Microsoft Bing allows an unauthorized attacker to execute code over a network
Deeper analysisAI
CVE-2025-21355 is a missing authentication for a critical function vulnerability affecting Microsoft Bing. Published on 2025-02-19, it carries a CVSS v3.1 base score of 8.6 (AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N) and maps to CWE-306 (Missing Authentication for Critical Function), with additional NVD-CWE-noinfo classification.
An unauthorized attacker with network access can exploit this vulnerability due to low attack complexity, requiring no privileges, user interaction, or special conditions. Successful exploitation allows remote code execution, achieving high confidentiality impact with a change in scope.
The Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21355 provides details on mitigation and patches.
Details
- CWE(s)