Quick answers
- Is This vulnerability exploited in the wild?
- No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
- How severe is This vulnerability?
- Critical severity, with a CVSS score of 9.8, published 11 August 2026.
- Which products and versions are affected?
- Microsoft MsQuic < 2.4.19; Microsoft.Native.Quic.MsQuic.OpenSSL (NuGet) < 2.4.19.
- Is there a fix for This vulnerability?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is This vulnerability attacked?
- It is attacked over the network.
- Am I affected?
- Check whether you run Microsoft MsQuic or Microsoft.Native.Quic.MsQuic.OpenSSL (NuGet) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A use-after-free vulnerability (CWE-416) exists in Microsoft QUIC that allows an unauthenticated network attacker to achieve remote code execution. The vulnerability occurs when memory is freed but subsequently accessed through a stale pointer, potentially allowing an attacker to control the reused memory location. Attack vector is network-based with low complexity, no authentication required, and no user interaction necessary. An attacker can craft malicious QUIC protocol packets to trigger the flaw and execute arbitrary code. Microsoft Native QUIC library versions before 2.4.19 are affected. Patch availability: no patched versions are listed in the advisory, though the version constraint suggests patches may be available beyond 2.4.19.
Affected products
- Microsoft Native QUIC (MsQuic) with OpenSSL < 2.4.19
Timeline
- 2026-08-11: disclosed