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CVE-2026-80971

ALSA: bcd2000: clear the URB pointers on disconnect

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: ALSA: bcd2000: clear the URB pointers on disconnect bcd2000_free_usb_related_resources() frees both URBs and leaves the pointers behind: usb_kill_urb(bcd2k->midi_out_urb); usb_kill_urb(bcd2k->midi_in_urb); usb_free_urb(bcd2k->midi_out_urb); usb_free_urb(bcd2k->midi_in_urb); The rawmidi device outlives that call. A substream that is still open when the device is unplugged reaches bcd2000_midi_send() from the trigger path on close. That function writes to the freed URB and then hands it to the USB core: bcd2k->midi_out_urb->transfer_buffer_length = BUFSIZE; ... ret = usb_submit_urb(bcd2k->midi_out_urb, GFP_ATOMIC); usb_kill_urb() does not stop a later submission either, so a submit that races the disconnect can requeue the URB after it has been reaped. midi_in_urb is exposed the same way: bcd2000_input_complete() resubmits it from the completion handler. KASAN on 7.2.0-rc5 (arm64): BUG: KASAN: slab-use-after-free in bcd2000_midi_send [snd_bcd2000] Write of size 4 at addr ffff00001827d388 by task bpoc/168 __asan_store4 bcd2000_midi_send [snd_bcd2000] bcd2000_midi_output_trigger [snd_bcd2000] snd_rawmidi_kernel_write1 close_substream.part.0 Freed by task 168: usb_free_urb bcd2000_disconnect [snd_bcd2000] BUG: KASAN: slab-use-after-free in usb_submit_urb Read of size 8 at addr ffff00001827d3b8 by task bpoc/168 Clear both pointers after freeing and test them on the paths that can still run. Poison the URBs before freeing them: usb_poison_urb() waits for a running completion handler and rejects any later submission, so after it returns the input path is quiesced and only the rawmidi trigger path can still reach bcd2000_midi_send(). No unpoison is needed; the URBs are freed on the next line. Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From b47a22290d581277be70e8a597824a4985d39e83 · fixed in 9af08677aa57debaca5b57c8045c52a83d3dd376; From b47a22290d581277be70e8a597824a4985d39e83 · fixed in 5a77febac6faf6da40fbb4555f703eeb91b58130; From b47a22290d581277be70e8a597824a4985d39e83 · fixed in 3c00004f134fc819f9d9e202c6a64acde0a1f8d0; From b47a22290d581277be70e8a597824a4985d39e83 · fixed in 6c07aad8a7c9ef8ebc4d03a964b882123a349a2e; From b47a22290d581277be70e8a597824a4985d39e83 · fixed in eb482a06791d6168beb8c78cc904ac5a5ed96a55; From b47a22290d581277be70e8a597824a4985d39e83 · fixed in 7df3194bdb7479cad9199889655a566a2c0c1d1b; From b47a22290d581277be70e8a597824a4985d39e83 · fixed in b06ebc7fe25a6af4a9f6e4a3d4236a4178ad4b01; From b47a22290d581277be70e8a597824a4985d39e83 · fixed in 459d3a64766f5ca2f1886daeaf24582831a5f5ab

  • Linux Linux

    3.16

  • KernelLinux

    From 3.16.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 8

git.kernel.org