UBUNTU-CVE-2026-80716: High severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: ALSA: pcm: wake linked drain waiters on unlink sndpcmdrain() on a linked stream parks an on-stack wait entry on the drained peer's runtime->sleep, and after scheduletimeout() removes it only if that peer is still found in the caller's group. If group membership changes during the wait and the sleep ends by signal or timeout (so autoremovewakefunction() does not run), finishwait() is skipped and sndpcmdrain() returns with the entry still queued on that stream's sleep list; a later wakeup() then walks a freed stack frame. This is reachable by unlinking either the drained or the draining stream. Unlike the close path (sndpcmdrop() -> sndpcmpoststop()), sndpcmunlink() never wakes the sleep queues. Wake every group member under the group lock before the membership change, so a linked drainer is released and drops its entry while the streams are still grouped. The window was opened when sndpcmlinkrwsem stopped being held across the wait and the removal became conditional on group membership (see Fixes). The later switch to finishwait() kept that conditional removal, so the signal/timeout case remained.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1117.124~20.04.1 - Upgrade
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ubuntu/linux-azure-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1123.132~20.04.1 - Upgrade
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ubuntu/linux-azure-fde-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1122.131~20.04.1 - Upgrade
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ubuntu/linux-gcp-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1118.128~20.04.1 - Upgrade
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ubuntu/linux-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-198.208~20.04.1 - Upgrade
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ubuntu/linux-ibm-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1111.115~20.04.1 - Upgrade
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ubuntu/linux-intel-iotg-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1112.118~20.04.1 - Upgrade
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ubuntu/linux-lowlatency-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-195.205~20.04.1 - Upgrade
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ubuntu/linux-oracle-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1114.120~20.04.1 - Upgrade
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ubuntu/linux-riscv-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1111.115~20.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 5.15.0-198.208 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 5.15.0-1117.124 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 5.15.0-1123.132 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 5.15.0-1122.131 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 5.15.0-1113.119 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 5.15.0-1100.108 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 5.15.0-1111.115 - Upgrade
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ubuntu/linux-intel-iotgto a version that resolves this vulnerability.Fixed in 5.15.0-1112.118 - Upgrade
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ubuntu/linux-kvmto a version that resolves this vulnerability.Fixed in 5.15.0-1109.114 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 5.15.0-195.205 - Upgrade
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ubuntu/linux-nvidiato a version that resolves this vulnerability.Fixed in 5.15.0-1112.113 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 5.15.0-1114.120 - Upgrade
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ubuntu/linux-xilinx-zynqmpto a version that resolves this vulnerability.Fixed in 5.15.0-1080.84 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 5.15.0-1101.103 - Upgrade
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ubuntu/linux-intel-iot-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1109.111 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 5.15.0-1116.125 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1117.124+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1123.132+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-198.208+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1118.128+fips1 - Compensating control
In snd_pcm_unlink(), while holding the group lock, wake every group member before changing group membership so linked drainers are released and remove their wait entries while the streams remain grouped.
Event History
Frequently Asked Questions
What conditions are required to trigger this issue?
An attacker needs local access with low privileges and must be able to manipulate linked ALSA PCM streams. The race is reachable by unlinking either the stream being drained or the stream performing the drain while snd_pcm_drain() is waiting.
What is the likely impact if the race is triggered?
A later wake-up can traverse a wait-list entry left behind on a freed stack frame. The supplied severity vector rates the impact as high for confidentiality, integrity, and availability of the vulnerable component.
Which Ubuntu kernel packages are identified as affected?
The listed packages are ubuntu/linux, ubuntu/linux-aws-fips, ubuntu/linux-azure, ubuntu/linux-azure-fips, ubuntu/linux-fips, ubuntu/linux-gcp, ubuntu/linux-gcp-fips, ubuntu/linux-realtime, and ubuntu/linux-azure-fips.
What change addresses the race?
The fix wakes every member of the PCM group while holding the group lock before changing group membership. This releases linked drain waiters so they can remove their wait entries before the streams are unlinked.