CVE-2025-39962

// PoC for CVE-2025-39962 - Linux kernel rxrpc unsigned integer underflow // This PoC demonstrates the vulnerability concept by sending a malformed // RXGK ticket with insufficient length to trigger the integer underflow. #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/socket.h> #include <linux/af_rxrpc.h> // Simulated vulnerable function logic from net/rxrpc/rxgk_app.c void vulnerable_decode_ticket(unsigned int ticket_len, unsigned char *ticket_data) { // VULNERABLE: untrusted unsigned subtract // If ticket_len < 40 (10*4), this wraps around to a huge value unsigned int data_len = ticket_len - 10 * 4; printf("ticket_len=%u, calculated data_len=%u\n", ticket_len, data_len); // This would lead to out-of-bounds access if (data_len > 0) { printf("Attempting to read %u bytes - potential OOB!\n", data_len); // memcpy/memmove with underflowed length would cause kernel panic } } int main() { // Craft a ticket with length less than 40 to trigger underflow unsigned int malicious_len = 20; // Less than 10*4 = 40 unsigned char ticket[64] = {0}; printf("Triggering CVE-2025-39962 PoC...\n"); vulnerable_decode_ticket(malicious_len, ticket); // In real scenario, send this via AF_RXRPC socket to trigger kernel path printf("PoC completed - underflow demonstrated\n"); return 0; }

{"cve": {"id": "CVE-2025-39962", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2025-10-09T13:15:32.390", "lastModified": "2026-02-26T23:03:53.710", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc: Fix untrusted unsigned subtract\n\nFix the following Smatch static checker warning:\n\n net/rxrpc/rxgk_app.c:65 rxgk_yfs_decode_ticket()\n warn: untrusted unsigned subtract. 'ticket_len - 10 * 4'\n\nby prechecking the length of what we're trying to extract in two places in\nthe token and decoding for a response packet.\n\nAlso use sizeof() on the struct we're extracting rather specifying the size\nnumerically to be consistent with the other related statements."}], "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:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-787"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "6.16.9", "matchCriteriaId": "A29694A5-4AF1-4C6F-8828-187FA35BAC01"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*", "matchCriteriaId": "327D22EF-390B-454C-BD31-2ED23C998A1C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*", "matchCriteriaId": "C730CD9A-D969-4A8E-9522-162AAF7C0EE9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*", "matchCriteriaId": "39982C4B-716E-4B2F-8196-FA301F47807D"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:*", "matchCriteriaId": "340BEEA9-D70D-4290-B502-FBB1032353B1"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc5:*:*:*:*:*:*", "matchCriteriaId": "47E4C5C0-079F-4838-971B-8C503D48FCC2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.17:rc6:*:*:*:*:*:*", "matchCriteriaId": "5A4516A6-C12E-42A4-8C0E-68AEF3264504"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/2429a197648178cd4dc930a9d87c13c547460564", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/71571e187106631a8127f2dde780f35caa358d33", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}