HTTP.sys Remote Code Execution Vulnerability
CVE-2026-47291 is a critical remote code execution vulnerability in the Windows HTTP Protocol Stack (HTTP.sys). The flaw is described as an integer overflow or wraparound in HTTP.sys that can lead to a heap-based buffer overflow during packet processing. Microsoft states that an unauthenticated attacker can exploit the issue by sending a specially crafted packet to a targeted server using HTTP.sys. The vulnerability is network-reachable, requires no privileges, and does not require user interaction. Microsoft and related reporting indicate that systems using the default MaxRequestBytes registry value of 16384 bytes are not affected, while certain non-default configurations that increase this value may be vulnerable.
Are you exposed to this one?
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A critical remote code execution vulnerability in HTTP.sys that allows unauthenticated remote exploitation without user interaction on affected systems with non-default MaxRequestBytes settings.
A critical remote code execution vulnerability in Windows HTTP Protocol Stack (http.sys) caused by integer overflow or wraparound.
A remote code execution vulnerability in Windows HTTP.sys caused by an integer overflow or wraparound.
A critical remote code execution vulnerability in Windows HTTP.sys that allows unauthenticated remote compromise without user interaction and is described as potentially wormable.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.