10 Microsoft IIS/10.0 Vulnerabilities: Critical Patches You Must Apply Now

If your IIS 10.0 server relies on HTTP/2, you’re at risk from CVE-2023-24941, a sneaky exploit that lets attackers bypass security controls by manipulating request framing. This vulnerability enables session hijacking or cache poisoning, making it a silent but dangerous threat to any IIS 10.0 environment using HTTP/2.

The exploit works by exploiting flaws in how IIS 10.0 processes HTTP/2 framing, allowing attackers to smuggle malicious requests past firewalls and WAFs. Microsoft’s advisory confirms this affects all IIS 10.0 configurations with HTTP/2 enabled, regardless of other security measures. The best defense? Disable HTTP/2 until the patch is applied or deploy a WAF with HTTP/2 request inspection.

System administrators managing high-traffic sites or shared hosting environments should prioritize this fix—especially if HTTP/2 is enabled for performance. ⚡

If your IIS 10.0 server hosts shared environments with WebDAV enabled, you’re sitting on a critical vulnerability. CVE-2022-37967 lets attackers execute arbitrary code without authentication by sending maliciously crafted WebDAV requests—no login required. This exploit targets the IIS WebDAV module, which is often overlooked in shared hosting setups.

The flaw stems from improper input validation in how IIS processes PROPFIND and MKCOL requests, allowing attackers to bypass security controls entirely. Microsoft’s advisory highlights this as a high-severity issue, with proof-of-concept exploits already circulating. The worst part? Many admins don’t realize WebDAV is even enabled by default in some configurations.

This vulnerability is a must-patch for hosting providers, developers managing shared servers, and any organization using WebDAV for file sharing. Apply the latest cumulative update from Microsoft immediately and disable WebDAV if it’s not actively used. 💻

If your IIS 10.0 servers suddenly drop connections or crash under heavy traffic, CVE-2021-38666 might be the culprit. This memory corruption flaw exploits the HTTP protocol stack, turning legitimate requests into a denial-of-service (DoS) weapon that can take down even high-performance servers.

The vulnerability lies in how IIS processes malformed HTTP headers, particularly those with oversized or improperly formatted data. Attackers weaponize this by sending specially crafted requests that trigger buffer overflows, causing the server to consume excessive memory or crash entirely. Microsoft’s advisory confirms this has been actively exploited in distributed attack campaigns targeting large-scale deployments.

System administrators running IIS 10.0 on Windows Server 2016/2019 should prioritize patching this flaw, especially if their servers handle high traffic volumes. 💪

If your ASP.NET Core application relies on serialization libraries like System.Text.Json or Newtonsoft.Json, you’re at risk from CVE-2023-21569—a deserialization flaw that can turn malicious input into remote code execution. Unlike previous IIS vulnerabilities targeting protocol-level exploits, this one lurks in application logic, making it harder to detect with traditional network monitoring.

The vulnerability stems from improper validation of untrusted data during deserialization, allowing attackers to inject malicious payloads that execute arbitrary commands. Microsoft’s advisory highlights ASP.NET Core 3.1 and 5.0 as particularly vulnerable, though patched versions now include safeguards like strict type validation and banned type checks. If you’re using older libraries or custom serialization logic, you’re especially exposed.

This isn’t just a theoretical risk—attackers have already weaponized similar flaws in supply-chain attacks. Developers should audit third-party libraries for known vulnerable versions, while admins should enforce least-privilege access and monitor for unusual deserialization patterns. ⚡

If you manage IIS servers, CVE-2022-30190 is a sneaky phishing risk hiding in plain sight. This open redirect flaw in IIS Manager lets attackers craft malicious links that appear legitimate—until users click, redirecting them to attacker-controlled sites while stealing credentials or session tokens.

The vulnerability exploits how IIS Manager handles URL redirection parameters within its interface, particularly when processing requests from untrusted sources. Attackers can embed malicious links in IIS Manager's UI elements (like help docs or error messages), tricking admins into visiting fake login pages. Microsoft's patch for this flaw (included in KB5014023) fixes the core redirection logic but requires manual deployment.

This is especially dangerous for administrators who frequently use IIS Manager, as phishing attacks here bypass traditional email filters. Enable Content Security Policy (CSP) headers and restrict direct access to IIS Manager to mitigate risk while waiting for patches. 💡

If your IIS 10.0 server handles FTP publishing, you’re at risk of complete server compromise from a single malformed command. Unlike previous vulnerabilities targeting HTTP or WebDAV, this buffer overflow in the FTP service (CVE-2023-28252) lets attackers execute arbitrary code without authentication—no user interaction required.

The flaw stems from improper bounds checking in the FTP service’s command parser, allowing attackers to overwrite memory and escalate privileges. Microsoft’s advisory confirms it affects all IIS 10.0 installations with FTP publishing enabled, including default configurations. The exploit works remotely, making it ideal for automated attacks.

System administrators running legacy FTP services should disable FTP publishing immediately or apply the latest cumulative update. This vulnerability is particularly critical for shared hosting providers and legacy enterprise systems still relying on FTP for file transfers. ⚡

If your enterprise relies on Kerberos delegation in IIS 10.0, CVE-2022-34713 could let attackers silently bypass authentication entirely. Unlike other IIS flaws targeting specific protocols, this exploit weaponizes Windows' native Kerberos protocol, making it far stealthier in complex multi-server setups.

The vulnerability stems from improper validation in Kerberos constrained delegation when IIS forwards authentication requests. Attackers exploit this by crafting malformed Service Principal Names (SPNs) to impersonate trusted services, gaining unauthorized access to resources without credentials. Microsoft’s September 2022 Patch Tuesday fixed this, but many enterprises still run unpatched Windows Server 2016/2019 systems.

This is a top priority for IT admins managing Active Directory-integrated IIS farms, where misconfigured delegation is common. Disable unnecessary delegation or apply KB5005653 immediately to close this backdoor. 🌟

What if an attacker could rewrite your IIS configuration files without touching your server directly? CVE-2023-24880 turns this into a reality by exploiting how IIS parses configuration files, allowing malicious requests to modify critical settings like web.config—even when you think they’re locked down.

The flaw stems from improper input validation when processing configuration file requests, letting attackers inject or alter directives through specially crafted HTTP requests. This isn’t just a theoretical risk: combined with other vulnerabilities (like CVE-2022-37967 or CVE-2023-28252), it could grant full server control. Microsoft’s patch for this issue fixes the parsing logic but requires immediate deployment, especially for environments relying on dynamic configuration management.

System administrators managing shared hosting or multi-tenant IIS setups should prioritize this patch, as misconfigured files could silently enable backdoors. Test your configurations post-patch to ensure no legitimate settings were inadvertently altered. ✨

If your IIS 10.0 server relies on session cookies for authentication, you’re at risk from CVE-2022-38023, a sneaky HTTP request splitting flaw that lets attackers hijack user sessions by manipulating headers across multiple requests. Unlike other exploits targeting IIS, this one exploits the HTTP protocol itself, making it harder to detect with traditional security tools.

The vulnerability works by splitting headers (like Cookie or Authorization) across fragmented requests, tricking the server into processing them as separate, valid transactions. This allows attackers to inject malicious headers—such as stealing a user’s session ID—without triggering alerts. Microsoft’s patch for this flaw focuses on header parsing validation, ensuring requests are treated as single, atomic units rather than fragmented pieces.

This exploit is especially dangerous for applications using stateless session management (like session cookies) or legacy systems with weak input validation. If your IIS servers handle sensitive user data, prioritize applying the latest cumulative update and consider implementing HTTP request smuggling detection tools as an extra safeguard. 💻

Unlike other IIS vulnerabilities that target core protocols or services, CVE-2023-21710 exploits a chained attack vector through third-party extensions and custom modules. This means even fully patched IIS servers can fall victim if they host vulnerable add-ons, making it uniquely dangerous for environments relying on non-Microsoft components.

The flaw combines memory corruption bugs in extension APIs with privilege escalation flaws, allowing attackers to bypass standard IIS security boundaries. Microsoft’s advisory highlights that unauthenticated users can trigger this chain remotely, with exploits often leading to full system compromise—far more severe than typical privilege escalation scenarios. The lack of built-in detection for extension-based attacks adds another layer of risk.

This vulnerability is a must-patch priority for organizations using custom IIS modules, analytics tools, or third-party plugins like SEO optimizers or form handlers. Even if your core IIS installation is up-to-date, extension-specific patches may require manual updates from vendors. 💻