CVE-2026-89791— perf: Fix use-after-free when perf mmap() revival races with the last munmap()
Quick assessment
Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
In the Linux kernel, the following vulnerability has been resolved: perf: Fix use-after-free when perf mmap() revival races with the last munmap() perf_mmap_close() drops rb->mmap_count without holding event->mmap_mutex (the refcount_dec_and_test() right befor
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I. Basic Information for CVE-2026-89791
Vulnerability Information
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Vulnerability Title
perf: Fix use-after-free when perf mmap() revival races with the last munmap()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
perf: Fix use-after-free when perf mmap() revival races with the last munmap()
perf_mmap_close() drops rb->mmap_count *without* holding
event->mmap_mutex (the refcount_dec_and_test() right before the
refcount_dec_and_mutex_lock() of event->mmap_count). A concurrent
perf_mmap_rb() can slot its entire "revival" path into that window
(perf_mmap holds event->mmap_mutex for its whole duration, including
rb_alloc):
munmap side (perf_mmap_close) mmap side (perf_mmap_rb)
----------------------------------- --------------------------------
rb->mmap_count 1 -> 0 (no lock) (holds event->mmap_mutex)
inc_not_zero(rb->mmap_count) fails
ring_buffer_attach(event, NULL)
rb_alloc() + attach new rb
refcount_set(&event->mmap_count, 1)
lock; event->mmap_count 1 -> 0
ring_buffer_attach(event, NULL)
ring_buffer_put() -> frees the *new* rb
The revival's refcount_set(&event->mmap_count, 1) is an invisible
1 -> 1 write: the close frees the just-revived buffer although the
other process still has it mapped -- a page-level use-after-free
allowing local privilege escalation to root by any unprivileged user
(default kernel.perf_event_paranoid=2).
Swap the order of the two counter updates: event->mmap_count is
dropped first via refcount_dec_and_mutex_lock(), so its 1 -> 0
transition and the ring_buffer_attach() stay serialized with
perf_mmap(). rb->mmap_count == 0 then implies every event using the
buffer is detached already, so the result of the rb->mmap_count drop
can gate the remaining teardown directly and detach_rest is no longer
needed.
An earlier fix for this race from Kyle Zeng and David Lee takes
event->mmap_mutex around both counter updates [0]; here the not-last
close stays lockless.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Affected Products
II. Public POCs for CVE-2026-89791
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Other References for CVE-2026-89791 (3)
Same Patch Batch · Linux · 2026-09-16 · 276 CVEs total
| CVE-2026-89860 | scsi: qla2xxx: Initialize NVMe abort_work once at submission | |
| CVE-2026-89877 | media: saa7164: fix cleanup on resource allocation failure | |
| CVE-2026-89875 | media: ti: vpe: quiesce overflow recovery before freeing streams | |
| CVE-2026-89876 | media: tda18250: fix possible integer overflow | |
| CVE-2026-89874 | media: v4l2-async: avoid deleting unlinked ASC entry on link error | |
| CVE-2026-89872 | media: v4l2-fwnode: Fix fwnode leak in v4l2_fwnode_parse_link | |
| CVE-2026-89873 | media: v4l2-ctrls: validate HEVC EXT SPS RPS counts | |
| CVE-2026-89871 | media: video-i2c: fix kthread error pointer left in kthread_vid_cap on failure | |
| CVE-2026-89870 | media: zoran: Avoid freeing a registered video_device twice | |
| CVE-2026-89869 | media: qcom: iris: use disable_irq() during power-off | |
| CVE-2026-89868 | media: chips-media: wave5: Add timeout while stop_streaming | |
| CVE-2026-89867 | media: chips-media: wave5: Defer job_finish() only when a DEC_PIC was queued | |
| CVE-2026-89866 | media: chips-media: wave5: Resume device before setting EOS flag | |
| CVE-2026-89865 | scsi: qla2xxx: Zero SFP DMA buffer in FRU/I2C bsg handlers | |
| CVE-2026-89864 | scsi: qla2xxx: Bound i2c->length in I2C bsg handlers | |
| CVE-2026-89863 | scsi: qla2xxx: edif: Fix NULL pointer deref in RX SA delete check | |
| CVE-2026-89862 | scsi: qla2xxx: Fix BSG job leak on validate flash image error path | |
| CVE-2026-89861 | scsi: qla2xxx: Hold vport reference in qla24xx_report_id_acquisition() | |
| CVE-2026-89850 | scsi: qla2xxx: Don't query firmware state while chip is down | |
| CVE-2026-89848 | scsi: qla2xxx: Quiesce response IRQ before freeing request queue |
Showing top 20 of 276 CVEs. View all on vendor page → →
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