Harmonyos CVE-2026-34865

No special conditions — remote unauthenticated exploitation against default installations with the WEB module enabled. CVSS 4.0 vector (AV:N/AC:L/PR:N/UI:N) indicates network-accessible out-of-bounds write in web component affecting confidentiality and availability.

This vulnerability represents CRITICAL real-world risk requiring immediate attention. The CVSS v4.0 score of 10.0 is justified by the attack characteristics: network-accessible (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and complete cross-scope impact on confidentiality, integrity, and availability. The CVSS vector indicates exploitation can compromise both the vulnerable component and subsequent systems (S:X with high cross-scope metrics), suggesting sandbox escape or lateral movement potential. While no public exploit is identified at time of analysis and EPSS data is not provided, the technical characteristics make this vulnerability highly attractive to attackers: remotely exploitable, no authentication barrier, affects a core system module handling untrusted web content, and achieves full system compromise. The heap overflow nature (CWE-122) is well-understood by exploit developers, and modern exploit mitigation bypasses for heap corruption are documented. HarmonyOS deployment in IoT devices, wearables, and mobile platforms increases the attack surface. The combination of maximum CVSS score, no authentication requirement, network exposure, and cross-scope impact elevates this to tier-one remediation priority despite absence of confirmed active exploitation.

An unauthenticated remote attacker crafts a malicious web page or injects malicious content into legitimate web traffic targeting a HarmonyOS device. When the device's WEB module processes the crafted content (through browsing, WebView rendering, or background content processing), the attacker's payload triggers the heap-based buffer overflow, overwriting critical memory structures. The attacker achieves arbitrary code execution within the WEB module context, then leverages the cross-scope impact to escape sandboxing restrictions, gaining control over the device operating system. The attacker can exfiltrate sensitive data (contacts, messages, health data from wearables), install persistent malware, or pivot to attack other devices on the network. No user interaction is required beyond the device's normal web content processing.