{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74503", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.908Z", "datePublished": "2026-08-15T12:27:28.208Z", "dateUpdated": "2026-08-17T05:47:54.696Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:47:54.696Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: timer: Clear SNDRV_TIMER_IFLG_DEAD once the close completes\n\nsnd_timer_close_locked() marks an instance with SNDRV_TIMER_IFLG_DEAD\nand returns early when the flag is already set, but the flag is never\ncleared again. A completed close ends in remove_slave_links(), which\nleaves timeri->timer NULL, so a second close is already harmless through\nthe timer == NULL path; the early return can only be reached by an\ninstance that was opened again in between. For such an instance the\nclose unlinks nothing, so snd_timer_instance_free() frees an object that\nis still on timer->open_list_head, still on snd_timer_master_list if it\nwas opened with a slave key, still owns any adopted slaves, and still\nholds its timer and module references.\n\nsnd_seq_timer_open() reopens an instance exactly like that: it retries\nits fallback open on the same object after a failure that has already\nrun snd_timer_close_locked() internally. An unprivileged user with\naccess to /dev/snd/timer and /dev/snd/seq can force that failure, since\nsnd_timer_check_master() returns -EBUSY when a pending slave matches the\nnew master's (slave_class, slave_id) key and the target timer has\nreached max_instances, and SNDRV_TIMER_IOCTL_SELECT with dev_class =\nSNDRV_TIMER_CLASS_SLAVE keeps the caller-supplied dev_sclass, so a\nsequencer queue's key can be forged. The freed instance is afterwards\ndereferenced by any further snd_timer_open() on that timer, by\nsnd_timer_check_slave(), and by /proc/asound/timers, which faults on the\nstale ti->owner pointer.\n\nThe flag only has to be visible while the close is in progress, which is\nall its other users need. Clear it in remove_slave_links(), under the\nsame timer->lock that sets it, once the instance is off every list." } ], "metrics": [ { "cvssV3_1": { "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" }, "scenarios": [ { "lang": "en", "value": "AV:L - Exploitation requires local ioctl access to /dev/snd/timer and /dev/snd/seq to forge timer slave keys and drive snd_seq_timer_open() retry logic; there is no network, adjacent-wireless, or physical-device entry path.\nAC:L - The attacker fully controls the ioctl and sequencer queue sequence that forces the initial -EBUSY close, retries snd_timer_open() on the same instance, and later triggers free; no uncontrollable timing, memory layout, or rare kernel state is required beyond standard ALSA being enabled.\nPR:L - The fix commit and reachable ioctl paths require only an unprivileged local user with access to ALSA device nodes (/dev/snd/timer and /dev/snd/seq), typical on desktops, kiosks, and Android systems via the audio group or equivalent permissions, not real root in the init namespace.\nUI:N - Exploitation is self-contained through attacker-initiated timer SELECT ioctls and sequencer queue open/close operations; no victim interaction such as opening files, mounting filesystems, or clicking prompts is required.\nS:U - Impact is kernel memory corruption and potential local privilege escalation within the same kernel address space; it does not cross a VM, container, or IOMMU security boundary into a separate authority.\nC:H - A use-after-free of snd_timer_instance leaves dangling list pointers; freed memory can be reallocated and later dereferenced by snd_timer_open(), snd_timer_check_slave(), or /proc/asound/timers, enabling arbitrary kernel memory read primitives.\nI:H - The UAF frees a structure still linked on timer open/master lists while retaining timer and module references, allowing heap reuse and memory corruption that can be leveraged for arbitrary kernel writes or control-flow hijacking.\nA:H - Stale timer instance pointers are dereferenced during subsequent timer operations and /proc/asound/timers reads, causing kernel faults/oops; UAF reliably threatens crashes even before full exploitation." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "sound/core/timer.c" ], "versions": [ { "version": "586b219a22b1032b28b8bd356b963276c5e5bf53", "lessThan": "bb016091010ec401a06e6bdace0cd944ee03d371", "status": "affected", "versionType": "git" }, { "version": "f46093dd22969037beb1fce2e043f3236be41c92", "lessThan": "a26a2e52736f9e39843ca66a2e1ce6bf1adbcd1e", "status": "affected", "versionType": "git" }, { "version": "da3039e91d1f835874ed6e9a33ea19ee80c2cb92", "lessThan": "0c561fab50991df10b1e4daca25886c34a2a9c07", "status": "affected", "versionType": "git" }, { "version": "da3039e91d1f835874ed6e9a33ea19ee80c2cb92", "lessThan": "c2744d5f3aea474513fd2298daecb94a952ce441", "status": "affected", "versionType": "git" }, { "version": "60e73ab87b84bbd6bd7ddd1d16019a3a3705ab8f", "status": "affected", "versionType": "git" }, { "version": "6.12.94", "lessThan": "6.12.103", "status": "affected", "versionType": "semver" }, { "version": "6.18.36", "lessThan": "6.18.44", "status": "affected", "versionType": "semver" }, { "version": "7.0.13", "lessThan": "7.1", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "sound/core/timer.c" ], "versions": [ { "version": "7.1", "status": "affected" }, { "version": "0", "lessThan": "7.1", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.103", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.44", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.8", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.94", "versionEndExcluding": "6.12.103" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18.36", "versionEndExcluding": "6.18.44" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.1", "versionEndExcluding": "7.1.8" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.1", "versionEndExcluding": "7.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0.13" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/bb016091010ec401a06e6bdace0cd944ee03d371" }, { "url": "https://git.kernel.org/stable/c/a26a2e52736f9e39843ca66a2e1ce6bf1adbcd1e" }, { "url": "https://git.kernel.org/stable/c/0c561fab50991df10b1e4daca25886c34a2a9c07" }, { "url": "https://git.kernel.org/stable/c/c2744d5f3aea474513fd2298daecb94a952ce441" } ], "title": "ALSA: timer: Clear SNDRV_TIMER_IFLG_DEAD once the close completes", "x_generator": { "engine": "bippy-1.2.0" } } } }