CVE-2023-36435

MsQuic Remote Denial of Service Vulnerability

Workarounds

Beyond upgrading to the patched versions, there is no other workaround.

The MsQuic server will continue to leak memory until no more is available, resulting in a denial of service.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2023-36435 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.2.3); upgrading removes the vulnerable code path.

Kodem intelligence

The following patch was made:

• Fix Memory Leak from Multiple Decodes of TP - https://github.com/microsoft/msquic/commit/d364feeda0dd8b729eca6fef149c1ef98630f0cb

1. What is CVE-2023-36435? CVE-2023-36435 is a high-severity uncontrolled resource consumption vulnerability in Microsoft.Native.Quic.MsQuic.OpenSSL (nuget), affecting versions < 2.2.3. It is fixed in 2.2.3. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2023-36435? CVE-2023-36435 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2023-36435?
   • Microsoft.Native.Quic.MsQuic.OpenSSL (nuget) (versions < 2.2.3)
   • Microsoft.Native.Quic.MsQuic.Schannel (nuget) (versions < 2.2.3)
4. Is there a fix for CVE-2023-36435? Yes. CVE-2023-36435 is fixed in 2.2.3. Upgrade to this version or later.
5. Is CVE-2023-36435 exploitable, and should I be worried? Whether CVE-2023-36435 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-36435 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-36435?
   • Upgrade Microsoft.Native.Quic.MsQuic.OpenSSL to 2.2.3 or later
   • Upgrade Microsoft.Native.Quic.MsQuic.Schannel to 2.2.3 or later

Other vulnerabilities in Microsoft.Native.Quic.MsQuic.OpenSSL