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CVE-2026-89747 (GCVE-0-2026-89747)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:46 – Updated: 2026-09-13 06:33
VLAI
Title
tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
Summary
In the Linux kernel, the following vulnerability has been resolved: tracing: Fix use-after-free in trace_pipe read on sub-buffer order change Writing to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(), which frees every sub-buffer of the ring buffer, including the reader page, and replaces them with newly allocated ones. Readers of trace_pipe hold pointers into those pages. ring_buffer_peek() looks up an event under cpu_buffer->reader_lock but returns the event pointer after dropping the lock, and peek_next_entry() then calls ring_buffer_event_length() and ring_buffer_event_data() on it. If the sub-buffer order is changed in that window, the reader dereferences freed memory: BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430 Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002 Freed by: free_buffer_page kernel/trace/ring_buffer.c:398 [inline] ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444 buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221 Take trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change. This is the lock trace_pipe readers already hold across their entire peek-and-print loop, so the swap can no longer race with a reader that is dereferencing a peeked event.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: f9b94daa542a8d2532f0930f01cd9aec2d19621b , < 05ebe1e1d7d38c2612bacfefe043a33572ae34cb (git)
Affected: f9b94daa542a8d2532f0930f01cd9aec2d19621b , < ddbe921ed16a0ad2d9e09574c3f3aabec7528325 (git)
Affected: f9b94daa542a8d2532f0930f01cd9aec2d19621b , < 7a49d19ff9baaf61217e5ec14199c18bc2d93ee4 (git)
Affected: f9b94daa542a8d2532f0930f01cd9aec2d19621b , < 372f8534244d632ad5118e8a87a11291b01712d3 (git)
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Linux Linux Affected: 6.8
Unaffected: 0 , < 6.8 (semver)
Unaffected: 6.12.109 , ≤ 6.12.* (semver)
Unaffected: 6.18.50 , ≤ 6.18.* (semver)
Unaffected: 7.2.4 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/trace.c"
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              "versionType": "original_commit_for_fix"
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                  "versionEndExcluding": "6.12.109",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix use-after-free in trace_pipe read on sub-buffer order change\n\nWriting to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(),\nwhich frees every sub-buffer of the ring buffer, including the reader\npage, and replaces them with newly allocated ones.\n\nReaders of trace_pipe hold pointers into those pages. ring_buffer_peek()\nlooks up an event under cpu_buffer-\u003ereader_lock but returns the event\npointer after dropping the lock, and peek_next_entry() then calls\nring_buffer_event_length() and ring_buffer_event_data() on it. If the\nsub-buffer order is changed in that window, the reader dereferences\nfreed memory:\n\n  BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430\n  Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002\n\n  Freed by:\n   free_buffer_page kernel/trace/ring_buffer.c:398 [inline]\n   ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444\n   buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221\n\nTake trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change.\nThis is the lock trace_pipe readers already hold across their entire\npeek-and-print loop, so the swap can no longer race with a reader that\nis dereferencing a peeked event."
        }
      ],
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            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
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              "value": "AV:L - The UAF is reached only via local tracefs: write() to buffer_subbuf_size_kb (buffer_subbuf_size_write -\u003e ring_buffer_subbuf_order_set) racing with read()/splice() of trace_pipe (tracing_read_pipe -\u003e ring_buffer_peek). No network, adjacent-radio, or physical-device path reaches this code.\nAC:L - The attacker controls both sides of the race: one thread reads trace_pipe while another writes buffer_subbuf_size_kb, which frees the reader page after dropping reader_lock. ring_buffer_peek then dereferences the stale event pointer; the attempt is retryable at will and CONFIG_TRACING is standard.\nPR:L - tracing_check_open_get_tr() checks only LOCKDOWN_TRACEFS and DAC, with no capable() gate. buffer_subbuf_size_kb (0640) and trace_pipe (0440) are delegated via uid=/gid= mounts to tracing-group accounts on Android/Perfetto, ChromeOS, and developer systems, matching CVE-2025-38101 and CVE-2026-74634.\nUI:N - The attacker opens and reads their own trace_pipe and writes buffer_subbuf_size_kb from their own threads. No victim action, mount, or file open by another user is required.\nS:U - The use-after-free corrupts kernel ring-buffer pages and metadata inside the host kernel\u0027s security authority. It can yield local privilege escalation but does not cross a VM, IOMMU, container, or hardware trust boundary.\nC:H - ring_buffer_subbuf_order_set() frees reader-page sub-buffers while ring_buffer_peek() still holds a pointer into them; peek_next_entry() and print_trace_line() then read the freed event and copy it to userspace via trace_pipe, disclosing recycled kernel heap contents.\nI:H - Freed sub-buffer pages and buffer_page objects can be reallocated while the reader still consumes attacker-controlled type_len/payload and print_trace_line() dispatches on iter-\u003eent-\u003etype. This UAF heap corruption is exploitable for arbitrary kernel writes and control-flow hijack.\nA:H - Dereferencing the freed reader page in ring_buffer_peek()/ring_buffer_event_length() causes a kernel oops, which is the syzbot KASAN use-after-free. The attacker can retrigger that crash at will."
            }
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        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/372f8534244d632ad5118e8a87a11291b01712d3"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89747",
    "datePublished": "2026-09-11T19:46:52.268Z",
    "dateReserved": "2026-09-11T19:38:34.762Z",
    "dateUpdated": "2026-09-13T06:33:56.494Z",
    "state": "PUBLISHED"
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      "date": "2026-09-15",
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    },
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-16T06:24:25+00:00",
      "cve": "CVE-2026-89747",
      "id": "CVE-2026-89747",
      "initial_release_date": "2026-09-11T00:00:00+00:00",
      "product_status:known_affected": "78",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: tracing: Fix use-after-free in trace_pipe read on sub-buffer order change",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89747.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-13T16:56:30Z",
      "cve": "CVE-2026-89747",
      "id": "CVE-2026-89747",
      "initial_release_date": "2026-09-12T16:22:21Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89747",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89747.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.