CVE-2021-1048
Android Kernel Use-After-Free Vulnerability
Description
CVE-2021-1048 is a use-after-free vulnerability in the Android kernel that allows for local privilege escalation. The vulnerability exists in the kernel's handling of file descriptors, where a race condition can lead to a use-after-free condition that an attacker can leverage to escalate privileges from a standard application context to kernel-level access. Successful exploitation does not require user interaction and can grant an attacker full control over the affected Android device. CISA has added CVE-2021-1048 to its KEV catalog, and the EPSS percentile of 81.8% indicates significant exploitation probability.
KEV Information
CVSS Score
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| android | - |
Multiple CVSS Assessments
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
References
- https://source.android.com/security/bulletin/2021-11-01(Patch, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1048(Third Party Advisory, US Government Resource)
Weakness Type
CWE-416: Use After Free
CWE-416 describes a weakness where a product references memory after it has been freed, potentially leading to program crashes, unexpected behavior, or code execution. In CVE-2021-1048, the Android kernel improperly handles certain file descriptor operations, creating a use-after-free condition that allows a local attacker to corrupt kernel memory and achieve privilege escalation.
Learn more: CWE-416 — Use After Free
Impact Analysis
CVE-2021-1048 enables local privilege escalation on Android devices, allowing an attacker with local code execution to gain kernel-level privileges. The vulnerability requires no user interaction, meaning a malicious application can exploit it silently in the background. Once kernel access is achieved, the attacker gains complete control over the device, including the ability to bypass Android's security sandbox, access all user data, install persistent backdoors, and intercept communications. The EPSS percentile of 81.8% reflects significant exploitation probability. CISA has confirmed active exploitation and added CVE-2021-1048 to the KEV catalog. The vulnerability is particularly concerning because it affects the core Android kernel, impacting a broad range of device manufacturers and models.
Exploit Maturity
CISA has confirmed active exploitation of CVE-2021-1048 in the wild and added it to the Known Exploited Vulnerabilities catalog with a remediation deadline of June 13, 2022. The EPSS percentile of 81.8% indicates significant exploitation probability. Google acknowledged exploitation in the November 2021 Android security bulletin, noting that the vulnerability may have been under limited, targeted exploitation. Use-after-free vulnerabilities in the Android kernel are high-value targets for commercial spyware vendors and advanced threat actors, as they provide a reliable path from application-level access to full kernel control on mobile devices.
Remediation
- Apply Android security updates as specified by the device manufacturer and Google. The November 2021 Android security patch level addresses CVE-2021-1048. This is the required action per CISA's KEV catalog.
- Ensure that automatic security updates are enabled on all Android devices to receive kernel patches as soon as they are available from device manufacturers.
- Restrict the installation of applications to trusted sources (Google Play Store) and enable Google Play Protect to scan for potentially harmful applications.
- Deploy mobile device management (MDM) solutions in enterprise environments to enforce security update compliance and monitor device patch levels.
- For high-risk users, consider using Android devices from manufacturers with a track record of timely security updates, and keep devices on the latest available Android version.
Technical Details
CVE-2021-1048 is a use-after-free vulnerability in the Android kernel's file descriptor management code. The vulnerability is classified under CWE-416 (Use After Free) and occurs when a file descriptor is closed and its associated memory is freed, but a reference to the freed memory remains accessible through another code path. A local attacker can trigger a race condition that causes the kernel to access the freed memory, which can then be reallocated and populated with attacker-controlled data. By carefully controlling the content placed in the reallocated memory, the attacker can corrupt kernel data structures and redirect execution flow to achieve arbitrary code execution with kernel privileges. The attack vector is local, requiring code execution on the device (e.g., through a malicious application), but no user interaction is needed once the malicious code is running.
Frequently Asked Questions
Is CVE-2021-1048 being actively exploited?
Yes, CVE-2021-1048 has been actively exploited in targeted attacks. CISA has confirmed active exploitation and added it to the KEV catalog. Google noted potential limited, targeted exploitation in the November 2021 security bulletin. The EPSS percentile of 81.8% reflects significant exploitation probability.
What products are affected by CVE-2021-1048?
CVE-2021-1048 affects the Android kernel, impacting a wide range of Android devices from multiple manufacturers. The vulnerability is addressed in the November 2021 Android security patch level.
How do I fix CVE-2021-1048?
Apply the November 2021 or later Android security patch. Ensure automatic security updates are enabled and only install applications from trusted sources. See the Remediation section for additional measures.
How severe is CVE-2021-1048?
CVE-2021-1048 is a kernel use-after-free vulnerability with an EPSS percentile of 81.8%. It enables local privilege escalation to kernel level without user interaction, potentially granting complete device control. Its exploitation in targeted attacks underscores the severity for both individual users and enterprise mobile security.
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