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

mediumCVSS 5.9CVE-2026-62899

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

CSIRTS triage

vendor: Microsoft product: .NET Authentication bypass

What: HTTP request/response smuggling in .NET permits bypass of security features.
Who is affected: Web applications and services using .NET that handle HTTP requests over networks.
Urgency: Medium severity (CVSS 5.9); not exploited but security feature bypass warrants timely remediation.
Action: Update to the patched version of .NET released by Microsoft.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 5.9
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62899

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-628990.71% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 50% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-62899	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.