CVE-2026-27766: OpenHarmony Information Disclosure Flaw

CVE-2026-27766 Overview

CVE-2026-27766 is an information disclosure vulnerability affecting OpenHarmony version 6.0 and prior releases. The flaw stems from a signal handler race condition [CWE-364] that a local, authenticated attacker can exploit to leak sensitive information from the operating system.

Exploitation requires local access with low privileges and no user interaction. The vulnerability impacts confidentiality without affecting integrity or availability of the affected system. OpenHarmony is a distributed operating system maintained by the OpenAtom Foundation and widely deployed across smart devices, IoT endpoints, and embedded platforms.

Critical Impact

A local attacker with low privileges can trigger a race condition in OpenHarmony v6.0 to read sensitive memory contents, exposing data that should remain confined to higher-privileged contexts.

Affected Products

• OpenHarmony v6.0
• OpenHarmony prior versions to v6.0
• Devices and platforms built on the affected OpenHarmony releases

Discovery Timeline

• 2026-05-19 - CVE-2026-27766 published to NVD
• 2026-05-19 - Last updated in NVD database

Technical Details for CVE-2026-27766

Vulnerability Analysis

The vulnerability is classified under [CWE-364] Signal Handler Race Condition. Signal handler race conditions occur when an asynchronous signal interrupts a non-reentrant code path, allowing inconsistent state to be observed or manipulated. In OpenHarmony v6.0 and earlier, this weakness permits a local attacker to leak information by racing the handler against ordinary execution.

The attack requires local access with low privileges and no user interaction. Confidentiality is impacted while integrity and availability remain unaffected. The narrow scope limits this to information disclosure rather than code execution or privilege escalation.

The upstream OpenHarmony security disclosure tracks the issue but does not publish detailed root-cause analysis publicly. Technical specifics on the affected component remain limited to the vendor advisory.

Root Cause

The root cause is a race condition in a signal handler path within OpenHarmony. Non-atomic operations or use of non-async-signal-safe functions inside the handler create a window where memory contents or process state can be observed by the attacker before sanitization completes.

Attack Vector

An attacker with a local account on the device triggers the vulnerable code path while issuing signals at precise intervals. Successful timing of the race allows the attacker to read memory regions or state information that would normally be inaccessible to their privilege level. No network access, user interaction, or elevated privileges are required beyond standard local user permissions.

No public proof-of-concept code is available. The OpenHarmony Security Disclosure provides the authoritative reference. See the OpenHarmony Security Disclosure for vendor-provided details.

Detection Methods for CVE-2026-27766

Indicators of Compromise

• Unexpected signal delivery patterns to processes handling sensitive data on OpenHarmony devices
• Local user processes repeatedly invoking system calls associated with vulnerable signal handlers
• Anomalous reads of process memory or state correlated with signal-driven execution

Detection Strategies

• Monitor audit logs for high-frequency signal generation by non-system local accounts on OpenHarmony endpoints
• Baseline normal signal-handler invocation rates and alert on statistical deviations indicating race-condition probing
• Correlate local process activity with access to sensitive data paths or kernel interfaces

Monitoring Recommendations

• Enable verbose process auditing on OpenHarmony devices where feasible
• Track local logon events and unusual privilege transitions on embedded and IoT fleets
• Forward device telemetry to a centralized data lake for cross-device correlation and retrospective hunting

How to Mitigate CVE-2026-27766

Immediate Actions Required

• Inventory all OpenHarmony devices and confirm running versions against the affected range
• Restrict local account provisioning on affected devices to trusted users only
• Apply the vendor patch referenced in the OpenHarmony security disclosure once available for your distribution

Patch Information

Refer to the OpenHarmony Security Disclosure for patch availability and version guidance. Upgrade to a fixed release beyond OpenHarmony v6.0 once published by the vendor or device OEM.

Workarounds

• Limit local shell or application access on affected devices to reduce the attacker population
• Apply mandatory access control policies to confine processes that interact with vulnerable signal-handling code
• Disable or restrict unnecessary services that allow local code execution on production OpenHarmony devices

# Configuration example: restrict local user shell access on affected devices
# Review accounts authorized for interactive login
getent passwd | awk -F: '$7 !~ /(nologin|false)/ {print $1}'

# Lock non-essential local accounts until patched
usermod -L <username>