CVE-2026-69623: Windows HTTP Print Provider Buffer Overflow

CVE-2026-69623 Overview

CVE-2026-69623 is a heap-based buffer overflow [CWE-122] in the Windows HTTP Print Provider. An authorized attacker can exploit the flaw to execute code over a network against a vulnerable Windows system. Exploitation requires low privileges and user interaction, but the vulnerability affects all three security pillars: confidentiality, integrity, and availability.

Microsoft published the advisory on 2026-09-08 and last updated it on 2026-09-09. The Exploit Prediction Scoring System (EPSS) currently rates the exploitation likelihood in the mid-range for recently published Microsoft vulnerabilities.

Critical Impact
Successful exploitation grants remote code execution within the context of the Windows HTTP Print Provider, enabling attackers to run arbitrary code on the target host.

Affected Products

Microsoft Windows (HTTP Print Provider component)
Specific affected builds are enumerated in the Microsoft Security Update Guide entry for CVE-2026-69623
Refer to Microsoft's advisory for the authoritative list of impacted SKUs and build numbers

Discovery Timeline

2026-09-08 - CVE-2026-69623 published to the National Vulnerability Database
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-69623

Vulnerability Analysis

The vulnerability resides in the Windows HTTP Print Provider, the component responsible for handling Internet Printing Protocol (IPP) requests over HTTP. A heap-based buffer overflow occurs when the provider processes attacker-controlled input without proper bounds validation. Writing past the allocated heap buffer corrupts adjacent memory structures.

An attacker who successfully exploits the flaw can execute arbitrary code within the process context of the print provider. Because the attack traverses the network and targets a system service, exploitation can lead to lateral movement, credential theft, and persistent footholds inside the target environment.

Root Cause

The root cause is improper validation of input length or size prior to a heap allocation or copy operation inside the HTTP Print Provider. When the calculated or attacker-supplied size exceeds the destination buffer, adjacent heap metadata and objects are overwritten. This corruption can be shaped into a control-flow hijack primitive.

Attack Vector

The attack vector is network-based. An authenticated user with low privileges sends a crafted HTTP request to the vulnerable print provider endpoint. User interaction is required, which typically means the victim must trigger or accept a print-related action. Successful exploitation yields code execution on the target host.

// No verified proof-of-concept code is publicly available for CVE-2026-69623.
// See the Microsoft Security Update Guide entry for technical details:
// https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69623

Detection Methods for CVE-2026-69623

Indicators of Compromise

Unexpected child processes spawned by the Windows Print Spooler or HTTP Print Provider service
Anomalous outbound network connections originating from print-related processes
Crashes or restart events for the Print Spooler service correlated with inbound HTTP print traffic
New or modified files under %SystemRoot%\System32\spool\ outside of scheduled print jobs

Detection Strategies

Monitor HTTP traffic to Internet Printing Protocol endpoints for oversized headers, malformed IPP attributes, or unusual request bodies
Alert on process lineage anomalies where the Print Spooler service launches command interpreters, scripting engines, or LOLBins
Correlate authentication events with subsequent print-service activity to identify low-privileged users targeting print infrastructure

Monitoring Recommendations

Enable verbose logging for the Print Spooler and HTTP print components on servers that expose printing over the network
Ingest print service telemetry into a centralized SIEM for cross-host correlation
Track heap corruption crash signatures via Windows Error Reporting to identify exploitation attempts

How to Mitigate CVE-2026-69623

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-69623 as soon as possible
Inventory all Windows systems exposing the HTTP Print Provider and prioritize patching internet-facing or high-privilege hosts
Restrict network access to print services so that only authorized print clients can reach the HTTP Print Provider endpoints

Patch Information

Microsoft has released fixes through the standard Windows security update channels. Consult the Microsoft Security Update Guide entry for CVE-2026-69623 for the specific Knowledge Base articles that apply to each affected Windows version and deploy them through Windows Update, WSUS, or your preferred patch management platform.

Workarounds

Disable the HTTP Print Provider or the Internet Printing Client feature on systems that do not require network printing over HTTP
Block inbound HTTP and HTTPS traffic to print server endpoints at the network perimeter and internal segmentation boundaries
Enforce least-privilege access to reduce the population of authenticated users capable of reaching the vulnerable endpoint

bash

# Disable the Internet Printing Client feature on Windows (run as administrator)
Dism /Online /Disable-Feature /FeatureName:Printing-Foundation-InternetPrinting-Client

# Stop and disable the Print Spooler service where printing is not required
Stop-Service -Name Spooler -Force
Set-Service -Name Spooler -StartupType Disabled