Description

Error in handling the PlatformLangCodes UEFI variable could cause a buffer overflow, leading to resource exhaustion and failure.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.7",
  "pubDate": "2026-09-03T13:04:12.283Z",
  "pubdate": "2026-09-03T13:04:12.283Z",
  "executiveSummary": "A critical memory corruption vulnerability exists in the UEFI firmware's handling of the PlatformLangCodes variable. This vulnerability is classified as a buffer overflow, which can be triggered during the processing of non-volatile UEFI variables.\nSuccessful exploitation of this flaw leads to resource exhaustion, resulting in a system crash or a denial-of-service (DoS) condition. Because the vulnerability resides within the UEFI environment, it operates beneath the operating system layer, complicating traditional security monitoring and remediation efforts.\nThe vulnerability poses significant risk to system stability and availability. An attacker capable of modifying non-volatile UEFI storage variables—typically requiring high-level privileges or physical access to the SPI flash interface—could manipulate these values to induce memory corruption.\nThe attack does not necessarily require network connectivity, as it is rooted in local firmware variable management. The primary impact is the loss of system availability and the potential for a persistent failure state until the variable is sanitized or the firmware is reflashed.\nThis vulnerability highlights the critical need for rigorous input validation and bounds checking when processing UEFI configuration data to prevent memory-based exploits.",
  "technicalDetails": "The vulnerability originates from improper bounds checking during the parsing and copying of the PlatformLangCodes UEFI variable. This variable, which is intended to store a list of supported language codes for the firmware interface, is processed by the UEFI firmware services during the pre-boot initialization phase.\nThe root cause is a classic buffer overflow condition where the data provided to the UEFI variable service exceeds the allocated destination buffer size. Because UEFI services often lack modern exploit mitigations like Address Space Layout Randomization (ASLR) or Data Execution Prevention (DEP) in earlier implementation stages, providing a maliciously crafted, oversized string to PlatformLangCodes causes the firmware to write beyond the intended memory boundaries.\nThe attack flow proceeds as follows: First, an attacker with appropriate privileges (such as kernel-mode access or via an accessible firmware interface) writes an excessively long string to the PlatformLangCodes variable in the non-volatile storage. Upon the subsequent system reset or power cycle, the firmware's variable parsing routine attempts to load and validate this malformed data.\nDuring this process, the firmware allocates a static buffer on the stack or heap to copy the contents of the variable. Due to the lack of sufficient length verification, the copy operation triggers a buffer overflow, overwriting adjacent memory structures or critical firmware control flow pointers.\nThe immediate post-exploitation impact is resource exhaustion or a memory access violation. This corruption causes the UEFI firmware to enter an unstable state, typically resulting in an immediate system hang, a kernel panic during the transition to the OS loader, or a continuous boot-loop.\nBecause the PlatformLangCodes variable is stored in NVRAM (non-volatile RAM), the exploitation is persistent. The system may fail to boot successfully until the problematic variable is cleared or overwritten by a recovery mechanism. In highly specific scenarios, depending on the firmware architecture and compiler-added protections, this type of overflow might theoretically lead to arbitrary code execution within the System Management Mode (SMM) or the UEFI execution environment, although the primary documented impact is denial-of-service.\nExposure is limited to systems where the firmware permits modification of NVRAM variables by authenticated software entities, or via direct manipulation of the SPI flash chip on the motherboard."
}