CVE-2011-1776 in Linux
Summary
by MITRE
The is_gpt_valid function in fs/partitions/efi.c in the Linux kernel before 2.6.39 does not check the size of an Extensible Firmware Interface (EFI) GUID Partition Table (GPT) entry, which allows physically proximate attackers to cause a denial of service (heap-based buffer overflow and OOPS) or obtain sensitive information from kernel heap memory by connecting a crafted GPT storage device, a different vulnerability than CVE-2011-1577.
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Analysis
by VulDB Data Team • 11/18/2021
The vulnerability described in CVE-2011-1776 represents a critical flaw in the Linux kernel's handling of EFI GUID Partition Table entries within the fs/partitions/efi.c file. This issue affects kernel versions prior to 2.6.39 and stems from insufficient validation of GPT entry sizes during the is_gpt_valid function execution. The vulnerability specifically targets the kernel's partition table parsing mechanism, which is responsible for identifying and processing storage device partition layouts according to the EFI specification. When a maliciously crafted GPT storage device is connected to a vulnerable system, the kernel's failure to properly validate the size of EFI GPT entries creates exploitable conditions that can lead to system instability or information disclosure.
The technical implementation of this vulnerability resides in the kernel's partition handling subsystem where the is_gpt_valid function processes EFI partition table entries without adequate bounds checking on the entry size fields. This oversight allows attackers with physical access to manipulate the size parameter of GPT entries in a way that causes the kernel to allocate insufficient memory for processing the entry, resulting in heap-based buffer overflows. The flaw specifically manifests when the kernel attempts to parse partition entries that exceed the expected size limits, causing memory corruption that leads to kernel oops (kernel panic) conditions and subsequent denial of service. The vulnerability is classified as a heap-based buffer overflow under CWE-121, which represents a classic memory safety issue where insufficient bounds checking allows for buffer overflows in heap-allocated memory regions.
The operational impact of this vulnerability extends beyond simple denial of service to include potential information disclosure from kernel heap memory. Attackers with physical proximity to target systems can exploit this weakness by connecting specially crafted storage devices that contain malformed GPT entries. The attack vector is particularly concerning because it requires only physical access to the target system, making it accessible to adversaries who can directly manipulate hardware components. The vulnerability creates conditions where kernel memory contents could be exposed to unauthorized parties, potentially revealing sensitive information such as cryptographic keys, system configuration details, or other confidential data stored in kernel memory spaces. This information disclosure aspect elevates the threat beyond simple service disruption to include potential compromise of system security and confidentiality.
Mitigation strategies for CVE-2011-1776 primarily involve upgrading to Linux kernel versions 2.6.39 or later where the vulnerability has been addressed through proper bounds checking in the is_gpt_valid function. System administrators should prioritize patching affected systems, particularly those in environments where physical security cannot be guaranteed or where unauthorized hardware access is possible. Additionally, implementing hardware security measures such as secure boot mechanisms and device access controls can provide additional layers of protection. The vulnerability demonstrates the importance of robust input validation in kernel space code and aligns with ATT&CK technique T1068 which covers the exploitation of privilege escalation vulnerabilities through kernel-level flaws. Organizations should also consider monitoring for suspicious partition table entries and implementing proper hardware inventory controls to prevent unauthorized storage device connections. The fix implemented in kernel versions 2.6.39 and later includes proper size validation that prevents the exploitation conditions described in this vulnerability, ensuring that GPT entries are properly validated before processing to prevent heap corruption and memory exposure scenarios.