CVE-2026-43141

/* * PoC for CVE-2026-43141 * This code simulates the condition that triggers the shift-out-of-bounds * vulnerability in the Linux kernel's ntb_hw_switchtec driver. * * Vulnerability context: * The kernel calls rounddown_pow_of_two(stdev->nr_direct_mw). * If nr_direct_mw is 0, undefined behavior occurs. */ #include <stdio.h> #include <stdint.h> // Simulate the specific kernel macro behavior for rounddown_pow_of_two #define roundup_pow_of_two(n) ( \ __builtin_constant_p(n) ? ( \ (n == 1) ? 1 : \ (1UL << (ilog2((n) - 1) + 1)) \ ) : \ __roundup_pow_of_two(n) \ ) // Simplified logic for demonstration of the fault unsigned long faulty_rounddown(unsigned long n) { // In the kernel, logic similar to (1UL << (fls(n) - 1)) is used // If n is 0, fls(0) is 0, resulting in 1 << -1 which is undefined. if (n == 0) { printf("[!] Triggering undefined behavior with input: 0\n"); // This line attempts the problematic operation return 1UL << (__builtin_clzl(n) - 1); } return 1UL << (31 - __builtin_clzl(n)); } int main() { printf("[*] CVE-2026-43141 PoC Simulation\n"); printf("[*] Simulating MW LUT count = 0\n"); // Trigger the vulnerable path faulty_rounddown(0); return 0; }

{"cve": {"id": "CVE-2026-43141", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-06T12:16:31.493", "lastModified": "2026-05-13T20:52:24.240", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nntb: ntb_hw_switchtec: Fix shift-out-of-bounds for 0 mw lut\n\nNumber of MW LUTs depends on NTB configuration and can be set to zero,\nin such scenario rounddown_pow_of_two will cause undefined behaviour and\nshould not be performed.\nThis patch ensures that rounddown_pow_of_two is called on valid value."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-125"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.15", "versionEndExcluding": "5.10.252", "matchCriteriaId": "0DACC27E-2C7E-4A63-8C6D-D02E7C1191F3"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.202", "matchCriteriaId": "4002FC2B-1456-4666-B240-0EBF590C4671"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.165", "matchCriteriaId": "797C7F46-D0BE-4FB8-A502-C5EF8E6B6654"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.128", "matchCriteriaId": "851E9353-6C09-4CC9-877E-E09DB164A3C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.75", "matchCriteriaId": "BCE16369-98ED-41CF-8995-DFDC10B288D2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.16", "matchCriteriaId": "B4B8CDA9-BADF-4CF5-8B3B-702DE8EEA40B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.6", "matchCriteriaId": "373EEEDA-FAA1-4FB4-B6ED-DB4DD99DBE67"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/186615f8855a0be4ee7d3fcd09a8ecc10e783b08", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/1a867d0d79a4a570a33f2f433919ad2bd7a27b67", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/2e4d5e8d86a969318340be95470bb76e52392082", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/5590cd04d6845c01a6bad985a491c58af6fb5389", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a11d03d116eef138a7249202bd772c8e61915aec", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a133e3caf844a3f56b6eef89ddaa66115874f6bd", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d0559d07afabfddaaded6a61a16154486b956764", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d652ef399f131fcd5f8f34266167449ee7c9e5b3", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}