CVE-2024-34740: Android Privilege Escalation Vulnerability

CVE-2024-34740 Overview

CVE-2024-34740 is a local privilege escalation vulnerability in Android's BinaryXmlSerializer.java component. The flaw resides in the attributeBytesBase64 and attributeBytesHex methods, where an integer overflow enables arbitrary XML injection. Google addressed the issue in the August 2024 Android Security Bulletin. The vulnerability affects Android versions 12, 12L, 13, and 14. Exploitation requires no user interaction and no additional execution privileges beyond a local context.

Critical Impact

A local attacker can trigger arbitrary XML injection through an integer overflow in BinaryXmlSerializer, resulting in escalation of privilege on affected Android devices.

Affected Products

• Google Android 12.0 and 12.1 (12L)
• Google Android 13.0
• Google Android 14.0

Discovery Timeline

• 2024-08-01 - Google publishes fix in the Android Security Bulletin
• 2024-08-15 - CVE-2024-34740 published to NVD
• 2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-34740

Vulnerability Analysis

The vulnerability exists in Android's binary XML serialization layer, specifically in BinaryXmlSerializer.java within the frameworks/base and modules-utils projects. The attributeBytesBase64 and attributeBytesHex methods write attribute payloads whose length is encoded as a bounded integer. When the input byte array exceeds the maximum representable length, arithmetic on the length field wraps, producing a value that no longer matches the actual data size.

Because the serializer trusts the truncated length while continuing to write the full attribute bytes, downstream consumers parse subsequent bytes as new XML structures. The attacker-controlled overflow bytes are interpreted as additional attributes, elements, or values, enabling arbitrary XML injection into system-managed XML files.

Root Cause

The root cause is an integer overflow ([CWE-190]) in the length handling of binary XML attribute writers, which enables XML injection ([CWE-91]). The serializer does not validate that attribute payloads remain within the bounds enforced by the on-wire length field before emitting the bytes. This mismatch between the declared length and the serialized payload allows an attacker to smuggle structured XML content past parser boundaries.

Attack Vector

Exploitation requires local access with low privileges, such as an installed third-party application. The attacker constructs a byte array whose size overflows the serializer's length field. When the crafted attribute is written into a system XML file — for example, a settings or package state file consumed by a privileged process — the injected XML modifies configuration owned by that higher-privileged context. This yields local escalation of privilege without user interaction. No public proof-of-concept exploit is available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

See the Android Security Bulletin August 2024 and the referenced source commits for the corrected length validation logic.

Detection Methods for CVE-2024-34740

Indicators of Compromise

• Unexpected modifications to system-managed binary XML files under /data/system/ or package state directories on unpatched devices.
• Presence of unusually large attribute payloads or malformed structures in binary XML artifacts produced by third-party apps.
• Local applications invoking BinaryXmlSerializer APIs with attribute byte arrays approaching Integer.MAX_VALUE in size.

Detection Strategies

• Inventory Android endpoints and identify devices whose security patch level predates 2024-08-01.
• Inspect mobile threat defense telemetry for applications that write oversized binary XML attributes or that trigger repeated crashes in system_server components handling XML state.
• Correlate privilege escalation indicators such as unexpected changes to system settings, package installer state, or permission grants with recent third-party app activity.

Monitoring Recommendations

• Enforce Android security patch level ≥ 2024-08-01 through mobile device management (MDM) compliance policies.
• Monitor installed applications for behaviors that write to shared system XML resources or invoke reflection against framework serializer APIs.
• Alert on package installations from untrusted sources on fleet devices still running Android 12, 12L, 13, or 14 without the August 2024 patch.

How to Mitigate CVE-2024-34740

Immediate Actions Required

• Apply the August 2024 Android security patch level (2024-08-01 or later) on all affected devices.
• Restrict sideloading and enforce Play Protect or equivalent vetting on managed devices until patches are deployed.
• Prioritize patch rollout for Android 12, 12L, 13, and 14 fleet devices, particularly those handling sensitive workloads.

Patch Information

Google released fixes in the Android Source Code Commit for frameworks/base and in the Android Modules Utils Update. Both commits add length validation to the attributeBytesBase64 and attributeBytesHex code paths. OEM builds incorporating the 2024-08-01 patch level are considered remediated. Consult the Android Security Bulletin August 2024 for OEM-specific guidance.

Workarounds

• No configuration workaround exists; the fix requires the vendor patch. Prioritize OEM update deployment.
• Reduce local attack surface by removing untrusted applications and enforcing MDM policies that block installation from unknown sources.
• Where devices cannot receive the patch, plan device replacement or upgrade to a maintained Android build.

# Verify the Android security patch level on a device via adb
adb shell getprop ro.build.version.security_patch
# Expected output for remediated devices: 2024-08-01 or later