CVE-2026-62899 — .NET Security Feature Bypass Vulnerability

Executive Summary

Inconsistent interpretation of http requests ('http request/response smuggling') in .NET allows an unauthorized attacker to bypass a security feature over a network.

Overview

5.9

CVSS MEDIUM

Important

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Security Feature Bypass

Released Aug 11 2026

Last Updated Aug 11 2026

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.00721 — 0.50787 percentile

NVD CVSS 5.9 MEDIUM — matches MSRC

CVSS Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C

ATTACK VECTOR

Network

ATTACK COMPLEXITY

High

PRIVILEGES REQUIRED

None

USER INTERACTION

None

SCOPE

Unchanged

CONFIDENTIALITY

High

INTEGRITY

None

AVAILABILITY

None

EXPLOIT CODE MATURITY

Unproven

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 5.2

EPSS Score

0.00721

probability of exploitation in the next 30 days

0.50787 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

10 affected products

Product	KB Article	Severity	Impact	Restart Required
.NET 10.0 installed on Linux	`5122106 (Security Update)`	Important	Security Feature Bypass	Maybe
.NET 10.0 installed on Mac OS	`5122106 (Security Update)`	Important	Security Feature Bypass	Maybe
.NET 8.0 installed on Linux	`5122104 (Security Update)`	Important	Security Feature Bypass	Maybe
.NET 8.0 installed on Mac OS	`5122104 (Security Update)`	Important	Security Feature Bypass	Maybe
.NET 8.0 installed on Windows	`5122104 (Security Update)`	Important	Security Feature Bypass	Maybe
.NET 9.0 installed on Linux	`5122105 (Security Update)`	Important	Security Feature Bypass	Maybe
.NET 9.0 installed on Mac OS	`5122105 (Security Update)`	Important	Security Feature Bypass	Maybe
.NET 9.0 installed on Windows	`5122105 (Security Update)`	Important	Security Feature Bypass	Maybe
Microsoft Visual Studio 2022 version 17.14	`(Security Update)`	Important	Security Feature Bypass	Unknown
Microsoft Visual Studio 2026 version 18.8	`(Security Update)`	Important	Security Feature Bypass	Unknown

Patches

4 patches

Article	Type	Restart
`5122106`	Security Update	Maybe
`5122104`	Security Update	Maybe
`5122105`	Security Update	Maybe
	Security Update	Unknown

Known Exploits

No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.

Acknowledgments

Miha Zupan with Microsoft

References

MSRC Advisory MITRE NVD