UBUNTU-CVE-2026-74278: Medium severity ubuntu/linux vulnerability
In the Linux kernel, the following vulnerability has been resolved: ALSA: seq: Fix kernel heap address leak in bounceerrorevent() The comment above bounceerrorevent() documents that user clients should receive SNDRVSEQEVENTBOUNCE with the original event embedded as variable-length data, while kernel clients should receive SNDRVSEQEVENTKERNELERROR with a quoted kernel pointer. However, the implementation unconditionally uses SNDRVSEQEVENTKERNELERROR with data.quote.event set to the raw struct sndseqevent pointer for all clients. When a bounce error event is delivered to a USERCLIENT via sndseqread(), the kernel heap address in data.quote.event is exposed to userspace through copytouser() in the fixed-length branch. This is a distinct leak path from the one addressed by commit 705dd6dcbc0e ("ALSA: seq: Clear variable event pointer on read"), which sanitizes data.ext.ptr in the variable-length branch of sndseqread(). The bounceerrorevent() leak uses fixed-length events that take the else branch where no sanitization occurs. Differentiate the bounce event by client type. For USERCLIENT, send SNDRVSEQEVENTBOUNCE with SNDRVSEQEVENTLENGTHVARIABLE and data.ext pointing to the original event. The variable-length path in sndseqeventdup() copies the event data into chained cells, and sndseqexpandvarevent() copies only the content -- never the pointer -- to userspace. For KERNELCLIENT, keep the existing SNDRVSEQEVENTKERNELERROR behavior with the quoted pointer.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-147.147 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70 - Upgrade
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-azure-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17~24.04.1 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 6.8.0-1069.76 - Upgrade
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ubuntu/linux-azure-fde-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1016.16~24.04.1 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 6.8.0-1066.74 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 6.8.0-1052.56 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38~24.04.4 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 6.8.0-1067.68 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-147.147.1 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1064.67 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1~24.04.1 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1033.38 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1062.63 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70+fips1 - Upgrade
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ubuntu/linux-azure-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-147.147+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-38.38 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1016.16 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1008.9 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Compensating control
Update ALSA sequencer bounce_error_event() to differentiate client type: for USER_CLIENT, send SNDRV_SEQ_EVENT_BOUNCE with SNDRV_SEQ_EVENT_LENGTH_VARIABLE and data.ext pointing to the original event; for KERNEL_CLIENT, retain SNDRV_SEQ_EVENT_KERNEL_ERROR with the quoted kernel pointer.
Event History
Frequently Asked Questions
Who can exploit this information leak?
A local attacker needs low-privileged access and the ability to act as an ALSA sequencer user client. The issue exposes a kernel heap address when a bounce error event is delivered through snd_seq_read().
What kernel configurations or Ubuntu package variants are in scope?
The affected software list includes Ubuntu linux, linux-fips, linux-aws, linux-azure, linux-gcp, and their listed FIPS cloud variants. The provided data does not identify a configuration requirement beyond use of the ALSA sequencer path.
How can I tell whether a system is exposed to the leak?
Exposure requires a USER_CLIENT to receive a bounce error event through the ALSA sequencer read path. The vulnerable behavior is a fixed-length SNDRV_SEQ_EVENT_KERNEL_ERROR event containing a raw struct snd_seq_event pointer copied to userspace.