EUVD-2026-35501
GHSA-392q-pc37-m552
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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ReconIdentify exposed Windows HTTP listener
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DeliveryCraft request with overflowing length field
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ExploitSend to HTTP.sys over TCP/80 or 443
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InstallInteger wrap undersizes kernel heap allocation
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C2Overwrite adjacent pool memory
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ExecuteHijack kernel control flow as SYSTEM
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ImpactDeploy implant or pivot internally
Vulnerability Assessment
| Weakness |
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Heap buffer bounds checking
MITRE ATT&CK
1 technique across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | No special conditions - remote unauthenticated exploitation against default configurations of any Windows host running an HTTP.sys-backed service reachable over the network, per the CVSS AV:N/AC:L/PR:N/UI:N vector. The practical limiting factor is exposure of an HTTP/HTTPS listener bound to HTTP.sys (IIS, WinRM over HTTP, WSDAPI, SSDP, or third-party services using the HTTP Server API) on a network path reachable from the attacker; hosts with no such listener bound, or with TCP/80 and TCP/443 firewalled to trusted sources only, are not exploitable. The description does not call out a specific protocol feature (e.g., HTTP/2, chunked encoding, range requests) as the trigger, so feature-level scoping cannot be confirmed from the available data. |
| Impact | All CVSS sub-metrics point to a top-tier risk: AV:N/AC:L/PR:N/UI:N means a remote, unauthenticated attacker can reach the bug over the network with low complexity, and C:H/I:H/A:H reflects full compromise of confidentiality, integrity, and availability. EPSS and SSVC values were not provided in the input, so probabilistic exploitation likelihood and automatability cannot be quantified here. The vulnerability is not listed in CISA KEV at the time of analysis and no public exploit code has been identified, which slightly tempers immediate urgency, but the kernel-mode attack surface and historical wormability of HTTP.sys bugs justify treating this as a P0 patching priority regardless of the absent telemetry. The single available reference is the Microsoft MSRC advisory, so detailed root-cause and exploit-status data beyond the description and CVSS vector are not independently confirmed. |
| Exploit ScenarioDerived | An attacker on the internet sends a single specially crafted HTTP request to a vulnerable IIS server or any Windows host exposing an HTTP.sys-backed listener, with header or chunked-body length fields chosen to wrap an internal size calculation. The undersized heap allocation is then overwritten by attacker-controlled bytes, corrupting kernel pool memory and ultimately yielding code execution in the SYSTEM context. No public exploit has been identified at the time of analysis, but the CVSS profile (AV:N/AC:L/PR:N/UI:N) and HTTP.sys history make pre-auth, scriptable mass exploitation plausible once a working trigger is published. |
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Alert meAnalysisAIv1 – Jun 09, 2026
Remote code execution in Microsoft Windows HTTP.sys allows unauthenticated network attackers to execute arbitrary code by triggering an integer overflow that leads to heap-based memory corruption. The flaw carries a CVSS 9.8 rating reflecting network reachability, no privileges, and no user interaction, and impacts the kernel-mode HTTP listener used by IIS and any Windows service relying on the HTTP Server API. No public exploit has been identified at the time of analysis and CISA KEV does not list it, but the wormable profile of HTTP.sys flaws warrants urgent patching.
RemediationAI
Apply the Microsoft security update referenced in the MSRC advisory (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-47291) for each affected Windows build as the primary fix; an exact fix version was not provided in the input data, so consult the advisory for the specific KB articles per SKU. Where patching cannot be completed immediately, restrict inbound TCP/80 and TCP/443 to HTTP.sys-backed services using host or network firewalls, terminate TLS and HTTP parsing on a non-Windows reverse proxy in front of IIS so malformed requests never reach the kernel driver, and disable optional HTTP.sys features such as HTTP/2 or response caching if the advisory identifies them as the trigger surface - note that proxy fronting can break NTLM/Kerberos pass-through and disabling HTTP/2 will reduce performance for modern clients. Audit and disable any unused HTTP Server API consumers (WinRM, WSDAPI, SSDP) on servers that do not require them.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 33 packages in microsoft, euvd
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
HTTP.sys is the Windows kernel-mode driver that parses and queues HTTP/HTTPS requests on behalf of IIS, WinRM, WSDAPI, SSDP, and various third-party services using the HTTP Server API. CWE-122 (Heap-based Buffer Overflow), triggered here through an integer overflow or wraparound in size calculations, occurs when arithmetic on a request-derived length wraps past INT_MAX or SIZE_MAX, causing a downstream allocation to be sized smaller than the data subsequently copied into it. Because HTTP.sys executes in kernel context (System), successful memory corruption typically yields SYSTEM-level code execution and is historically wormable, as seen in prior HTTP.sys issues such as CVE-2021-31166 and CVE-2022-21907.
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Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Integer overflow or wraparound in Windows HTTP.sys allows an unauthorized attacker to execute code over a network.
Articles & Coverage 1
Executive ViewAI
A critical remote code execution vulnerability in Windows HTTP.sys (CVE-2026-47291) exposes all IIS and HTTP Server API-dependent services to complete system compromise through unauthenticated network access, with no vendor patch currently available. The vulnerability's wormable characteristics mean rapid propagation is possible once exploitation begins. Organizations must immediately inventory affected systems and implement emergency compensating controls while awaiting vendor patching.
No vendor-released patch identified at time of analysis. Interim mitigations: restrict network access to HTTP.sys listeners through firewalls and network segmentation, deploy Web Application Firewall (WAF) rules on IIS endpoints, disable HTTP Server API services not operationally required, implement EDR tooling with monitoring for HTTP.sys process anomalies, and restrict administrative access to affected systems. These controls reduce but do not eliminate risk-emergency patching is critical upon vendor availability.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.
A heap overflow occurs when a program writes data beyond the bounds of a buffer allocated in the heap memory region.
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