GHSA-R7HX-2638-9JPM
Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-10-30 15:33In the Linux kernel, the following vulnerability has been resolved:
ALSA: seq: Don't leak the extension cell pointer in the bounce payload
The bounce_error_event() embeds the failed event in the bounce payload by pointing data.ext.ptr at it. When that event is a queued variable-length event, its own data.ext.ptr holds the address of its first extension cell, put there by snd_seq_event_dup(). The payload goes out verbatim through snd_seq_expand_var_event(), so the address reaches userspace.
That is the same address commit 705dd6dcbc0e ("ALSA: seq: Clear variable event pointer on read") removed from the event header. The read path still clears it there, just above the call that expands the payload.
Embed a sanitised copy instead, treated exactly as snd_seq_read() treats the header. A stack copy is enough because delivery is synchronous and snd_seq_event_dup() copies before returning.
An unprivileged client reaches this by setting SNDRV_SEQ_FILTER_BOUNCE, queueing a variable-length event to a port that does not exist and reading the bounce back. Eight bytes on 64-bit, from its own pool.
{
"affected": [],
"aliases": [
"CVE-2026-90220"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:17:17Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: seq: Don\u0027t leak the extension cell pointer in the bounce payload\n\nThe bounce_error_event() embeds the failed event in the bounce payload\nby pointing data.ext.ptr at it. When that event is a queued\nvariable-length event, its own data.ext.ptr holds the address of its\nfirst extension cell, put there by snd_seq_event_dup(). The payload\ngoes out verbatim through snd_seq_expand_var_event(), so the address\nreaches userspace.\n\nThat is the same address commit 705dd6dcbc0e (\"ALSA: seq: Clear\nvariable event pointer on read\") removed from the event header. The\nread path still clears it there, just above the call that expands the\npayload.\n\nEmbed a sanitised copy instead, treated exactly as snd_seq_read()\ntreats the header. A stack copy is enough because delivery is\nsynchronous and snd_seq_event_dup() copies before returning.\n\nAn unprivileged client reaches this by setting SNDRV_SEQ_FILTER_BOUNCE,\nqueueing a variable-length event to a port that does not exist and\nreading the bounce back. Eight bytes on 64-bit, from its own pool.",
"id": "GHSA-r7hx-2638-9jpm",
"modified": "2026-10-30T15:33:35Z",
"published": "2026-09-17T18:31:56Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90220"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/42c3f856d13a91a0d4c302a0c6854813621136db"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/59e1592d3c270ff4642d5d6dc55c545306eb0693"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6e6e471eef1d5d8cb056c7d364023fe048249204"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b1e8d40663997aacaa198f37ce6893e07aaba77a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c92b2e6e418a3885758438dddcead6e954a9e095"
}
],
"schema_version": "1.4.0",
"severity": []
}
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