CVE-2026-54000: osquery Privilege Escalation Vulnerability

CVE-2026-54000 Overview

CVE-2026-54000 is a heap-based buffer overflow [CWE-122] in osquery, an SQL-powered operating system instrumentation and monitoring framework. The vulnerability affects osquery versions prior to 5.23.1 running on Windows. A local unprivileged attacker can trigger an out-of-bounds heap write when the processes table queries a maliciously crafted process. The root cause is unchecked Process Environment Block (PEB) string lengths during reads of process command-line and current-directory fields. Successful exploitation may enable local privilege escalation from a standard user account to SYSTEM, because osquery typically runs as a privileged service.

Critical Impact
A local attacker can escalate from a standard Windows user to SYSTEM by exploiting the osquery processes table with a crafted PEB.

Affected Products

osquery on Windows prior to version 5.23.1
Deployments running the osquery daemon (osqueryd) as a privileged service
Environments where the processes table is enumerated on scheduled queries or ad-hoc packs

Discovery Timeline

2026-07-10 - CVE-2026-54000 published to NVD
2026-07-14 - Last updated in NVD database

Technical Details for CVE-2026-54000

Vulnerability Analysis

The flaw resides in the Windows implementation of the osquery processes table. When osquery enumerates processes, it reads the target process's PEB to extract command-line and current-directory strings. The Windows PEB exposes UNICODE_STRING structures whose Length and MaximumLength fields describe the buffer size. osquery trusted these values without validation. A local attacker who controls a process can craft PEB fields with attacker-chosen lengths, causing osquery to copy attacker-controlled data past the bounds of an allocated heap buffer. Because osqueryd typically runs as SYSTEM, the resulting heap corruption occurs inside a privileged process context.

Root Cause

The root cause is missing bounds validation on PEB UNICODE_STRING length fields prior to memory copy operations in the Windows processes table implementation. The fix, tracked in commit 3d457c412eb0c986b0c37d8903edae8bc9f9e246, refactors processes.cpp and introduces a dedicated processes.h header to enforce validated reads of remote process memory.

Attack Vector

Exploitation requires local access with the ability to launch a process. The attacker spawns a process with a manipulated PEB structure and waits for osquery to query the processes table. User interaction is required in the sense that a query must run against the malicious process, but scheduled query packs make this trivial in typical deployments.

cpp

// Patch: osquery/tables/system/windows/processes.cpp
#include <osquery/core/windows/wmi.h>
#include <osquery/sql/dynamic_table_row.h>
+#include <osquery/tables/system/windows/processes.h>
 #include <osquery/utils/conversions/join.h>
 #include <osquery/utils/conversions/tryto.h>
 #include <osquery/utils/conversions/windows/strings.h>

Source: osquery commit 3d457c4

Detection Methods for CVE-2026-54000

Indicators of Compromise

Unexpected crashes or Windows Error Reporting (WER) entries for osqueryd.exe on hosts running versions prior to 5.23.1
Creation of processes with abnormally large or malformed command-line and current-directory PEB fields
Standard-user processes followed shortly by new SYSTEM-level processes spawned from osqueryd.exe

Detection Strategies

Inventory all Windows endpoints running osquery and flag any version below 5.23.1
Alert on child processes of osqueryd.exe, which should rarely spawn interactive or shell processes
Correlate osqueryd.exe service crashes with recent process-creation events from non-administrative users

Monitoring Recommendations

Ingest Sysmon Event IDs 1 (process create), 10 (process access), and 11 (file create) for osqueryd.exe into a central data lake
Monitor Windows Service Control Manager events for repeated osqueryd restarts, which can indicate heap corruption attempts
Track integrity-level transitions where a standard-user session precedes SYSTEM process creation on the same host

How to Mitigate CVE-2026-54000

Immediate Actions Required

Upgrade all Windows osquery deployments to version 5.23.1 or later
Audit query packs and remove or restrict processes table queries until patched builds are deployed
Restrict local logon rights on servers running osqueryd to reduce the local-attacker population

Patch Information

The issue is fixed in osquery 5.23.1. Review the GitHub Security Advisory GHSA-4r78-6hg6-33gg, the osquery 5.23.1 release notes, the pull request discussion, and the patch commit for full technical details.

Workarounds

Disable scheduled queries that reference the processes table on Windows hosts until the upgrade is complete
Run osqueryd under a lower-privileged account where operationally feasible to reduce the impact of exploitation
Apply application-control policies to prevent unapproved standard-user binaries from executing on osquery-monitored hosts

bash

# Verify installed osquery version on Windows
osqueryi.exe --version

# Example: temporarily remove processes queries from a pack
# Edit the pack JSON and remove or comment queries referencing FROM processes
# Then reload the daemon
sc.exe stop osqueryd
sc.exe start osqueryd