Linux Kernel fb_mmap Integer Overflow Local Privilege Escalation Vulnerability (CVE-2013-2596)
Executive & SecOps Summary
SECOPS ASSESSMENTLinux kernel versions before 3.8.9, including certain Android 4.1.2 builds and embedded Linux systems
Local attackers can exploit an integer overflow to map the entire kernel memory space with read-write permissions, leading to full root privilege escalation
Upgrade the Linux kernel to version 3.8.9 or higher, and restrict access permissions to framebuffer device files
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Upgrade your Linux kernel to version 3.8.9 or the latest security patch provided by your distribution vendor.
# For Debian/Ubuntu systems
sudo apt-get update && sudo apt-get install --only-upgrade linux-image-generic -y
# For RHEL/CentOS systems
sudo yum update kernel -y
# Reboot the system to apply the new kernel
sudo reboot2. Temporary Workaround & Hardening Configuration
If patching is not immediately feasible, restrict access to the framebuffer device files to prevent non-privileged users from triggering the vulnerability.
# Restrict permissions on framebuffer devices to root only
sudo chmod 600 /dev/fb*
sudo chmod 600 /dev/graphics/fb* 2>/dev/null || true
# Persist permissions across reboots using udev rules
echo 'KERNEL=="fb*", MODE="0600", OWNER="root", GROUP="root"' | sudo tee /etc/udev/rules.d/99-monitor-privilege.rules
sudo udevadm trigger3. Log Audit & IoC Verification Commands
Verify the running kernel version and inspect system logs for suspicious framebuffer access attempts.
# Check the current running kernel version
uname -r
# Audit system logs for abnormal fb0 or mmap activities
sudo dmesg | grep -Ei 'fb0|fbmem|mmap'
sudo journalctl -k | grep -Ei 'fb0|fb_mmap'Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2013-2596) is an integer overflow (CWE-190) located in the fb_mmap function within drivers/video/fbmem.c of the Linux kernel. Due to insufficient boundary and validation checks on memory mapping size and offset calculations, an integer overflow can be triggered when processing user-supplied arguments.
2. Exploitation Mechanics & Attack Scenario
A local attacker can invoke the mmap2 system call on the framebuffer device file (such as /dev/graphics/fb0 or /dev/fb0) with crafted parameters. The resulting integer overflow bypasses the kernel's range validation checks, allowing the attacker to map arbitrary physical memory addresses—including the entire kernel memory space—into user space with read-write privileges. This technique was famously utilized by the 'Motochopper' exploit tool to root Android devices.
3. Infrastructure & Business Impact
As a local privilege escalation (LPE) vulnerability, successful exploitation allows an unprivileged local user or malicious application to obtain full root privileges. Given its inclusion in the CISA KEV catalog, this vulnerability poses a severe threat to multi-tenant environments, container hosts, and legacy embedded systems where local isolation is critical.
Official Vendor Advisories & References
Integer overflow in the fb_mmap function in drivers/video/fbmem.c in the Linux kernel before 3.8.9, as used in a certain Motorola build of Android 4.1.2 and other products, allows local users to create a read-write memory mapping for the entirety of kernel memory, and consequently gain privileges, via crafted /dev/graphics/fb0 mmap2 system calls, as demonstrated by the Motochopper pwn program.
Frequently Asked SecOps Questions (CVE-2013-2596)
FAQQ1. How critical is CVE-2013-2596 and is it actively exploited in the wild?
CVE-2013-2596 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 3.2%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2013-2596?
Primary impacted vendors include linux, motorola, google across linux_kernel, android. Scope summary: Linux kernel versions prior to 3.8.9 (including specific Android 4.1.2 Motorola builds and other Linux-based systems)
Q3. What temporary mitigations or workarounds exist for CVE-2013-2596 before patching?
[Mitigation] Upgrade the Linux kernel to version 3.8.9 or higher, and restrict access permissions to framebuffer device files Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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