CVE-2026-31691

/* * PoC Concept for CVE-2026-31691 * This code demonstrates the condition required to trigger the deadlock. * It sets up an AF_XDP socket in zero-copy mode. * To trigger the vulnerability, terminate this process abruptly (e.g., kill -9). */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <errno.h> #include <bpf/xsk.h> int main() { struct xsk_socket *xsk; struct xsk_umem *umem; struct xsk_ring_config rx_config = {0}; struct xsk_ring_config tx_config = {0}; // Configuration for zero-copy setup would go here // (Simplified for conceptual representation) printf("Starting AF_XDP zero-copy application...\n"); printf("Terminate this process with 'kill -9' to trigger the vulnerability.\n"); // In a real exploit, this would set up the UMEM and bind to the interface // then enter a loop processing packets. while(1) { // Simulating active polling/processing sleep(1); } return 0; }

{"cve": {"id": "CVE-2026-31691", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-27T18:16:54.610", "lastModified": "2026-05-06T20:49:04.757", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nigb: remove napi_synchronize() in igb_down()\n\nWhen an AF_XDP zero-copy application terminates abruptly (e.g., kill -9),\nthe XSK buffer pool is destroyed but NAPI polling continues.\nigb_clean_rx_irq_zc() repeatedly returns the full budget, preventing\nnapi_complete_done() from clearing NAPI_STATE_SCHED.\n\nigb_down() calls napi_synchronize() before napi_disable() for each queue\nvector. napi_synchronize() spins waiting for NAPI_STATE_SCHED to clear,\nwhich never happens. igb_down() blocks indefinitely, the TX watchdog\nfires, and the TX queue remains permanently stalled.\n\nnapi_disable() already handles this correctly: it sets NAPI_STATE_DISABLE.\nAfter a full-budget poll, __napi_poll() checks napi_disable_pending(). If\nset, it forces completion and clears NAPI_STATE_SCHED, breaking the loop\nthat napi_synchronize() cannot.\n\nnapi_synchronize() was added in commit 41f149a285da (\"igb: Fix possible\npanic caused by Rx traffic arrival while interface is down\").\nnapi_disable() provides stronger guarantees: it prevents further\nscheduling and waits for any active poll to exit.\nOther Intel drivers (ixgbe, ice, i40e) use napi_disable() without a\npreceding napi_synchronize() in their down paths.\n\nRemove redundant napi_synchronize() call and reorder napi_disable()\nbefore igb_set_queue_napi() so the queue-to-NAPI mapping is only\ncleared after polling has fully stopped."}], "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:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "6.18.23", "matchCriteriaId": "EA76AE25-9812-47C4-9714-A85435AEFA0F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.13", "matchCriteriaId": "1490EF9B-9080-481C-8D22-1306AAE664E4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/27f5997686ee7fb7ac01be72b2010f168a3409fc", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4700471775746058c962ded6e659bf908fd76e13", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/b1e067240379f950a0022208e0685f3465c211cb", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}