CVE-2020-14310 in grub2
Summary
by MITRE
There is an issue on grub2 before version 2.06 at function read_section_as_string(). It expects a font name to be at max UINT32_MAX - 1 length in bytes but it doesn't verify it before proceed with buffer allocation to read the value from the font value. An attacker may leverage that by crafting a malicious font file which has a name with UINT32_MAX, leading to read_section_as_string() to an arithmetic overflow, zero-sized allocation and further heap-based buffer overflow.
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Analysis
by VulDB Data Team • 03/18/2026
The vulnerability identified as CVE-2020-14310 resides within the grub2 bootloader software, specifically in the read_section_as_string() function that handles font name processing. This flaw represents a classic buffer overflow vulnerability that can be exploited through improper input validation and memory allocation handling. The issue affects grub2 versions prior to 2.06, making it a significant concern for systems that rely on older bootloader implementations. The vulnerability stems from the function's assumption that font names will not exceed UINT32_MAX - 1 bytes in length, creating a dangerous gap in input sanitization that attackers can exploit to manipulate memory allocation behavior.
The technical exploitation mechanism involves crafting a malicious font file containing a font name of exactly UINT32_MAX characters in length. When the read_section_as_string() function processes this input, it performs arithmetic operations that result in an arithmetic overflow condition, ultimately leading to a zero-sized buffer allocation. This memory allocation failure creates a heap-based buffer overflow scenario where subsequent memory operations can overwrite adjacent heap memory regions. The vulnerability operates at the intersection of multiple security concerns including improper input validation, arithmetic overflow, and heap corruption that can lead to arbitrary code execution. This type of vulnerability is classified under CWE-129 as "Improper Validation of Array Index" and CWE-190 as "Integer Overflow or Wraparound" according to the Common Weakness Enumeration framework.
The operational impact of this vulnerability extends beyond simple memory corruption, potentially enabling attackers to achieve privilege escalation or system compromise through carefully crafted font files. In bootloader contexts, this represents a critical attack surface since the bootloader executes with high privileges during system initialization. Attackers could leverage this vulnerability to inject malicious code into the boot process, potentially compromising the entire system before the operating system loads. The vulnerability is particularly concerning because it operates within the boot process where traditional security controls may be less effective. According to MITRE ATT&CK framework, this vulnerability maps to T1068 as "Exploitation for Privilege Escalation" and T1542.001 as "Pre-OS Boot" since it targets the boot process itself rather than the operating system runtime environment.
Mitigation strategies for CVE-2020-14310 primarily focus on upgrading to grub2 version 2.06 or later, which contains the necessary patches to address the buffer overflow conditions. System administrators should also implement font file validation policies that restrict the size and content of font files loaded during boot processes. Additional protective measures include enabling heap protection mechanisms such as stack canaries and address space layout randomization where possible. The vulnerability demonstrates the critical importance of input validation in security-critical code paths and serves as a reminder that bootloader components require rigorous security testing. Organizations should conduct thorough vulnerability assessments of their boot environments and ensure that all firmware and bootloader components are maintained at supported versions to prevent exploitation of similar arithmetic overflow vulnerabilities.