Summary
Impact: Security Feature Bypass. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
What kind of security feature could be bypassed by successfully exploiting this vulnerability?
An attacker who successfully exploited this vulnerability could smuggle another HTTP request and bypass front-end security controls or hijack other users' credentials.
According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability?
Successful exploitation of this vulnerability requires that the target system be set up in a specific manner and the attacker to have knowledge of that setup.
Security updates
10.0.11 — https://support.microsoft.com/help/5122106
8.0.30 — https://support.microsoft.com/help/5122104
9.0.19 — https://support.microsoft.com/help/5122105
Vulnerabilities 1
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Medium 5.9
.NET Security Feature Bypass Vulnerability
Inconsistent interpretation of http requests ('http request/response smuggling') in .NET allows an unauthorized attacker to bypass a security feature over a network.
Revision history
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#1
Information published.
References
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CVE-2026-62899 .NET Security Feature Bypass Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62899
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss