CVE-2026-99233 (GCVE-0-2026-99233)

Vulnerability from cvelistv5 – Published: 2026-11-02 16:06 – Updated: 2026-11-03 19:13
VLAI
Title
tracing/histograms: Verify event_call identity when updating synth_event refcount
Summary
In the Linux kernel, the following vulnerability has been resolved: tracing/histograms: Verify event_call identity when updating synth_event refcount In event_hist_trigger_parse() and hist_unreg_all(), the histogram registration and unregistration paths look up find_synth_event() using trace_event_name(file->event_call) and adjust se->ref if a match is found. Because find_synth_event() only compares the event basename, registering or removing a histogram on a non-synthetic trace event whose basename matches a synthetic event erroneously modifies the synthetic event's reference count. If a histogram is registered on the non-synthetic event before the synthetic event is created and removed afterwards, se->ref is decremented without a matching increment, allowing the synthetic event to be freed while an active histogram action still holds a pointer to it. Introduce find_synth_event_call() to verify that &se->call matches file->event_call before adjusting se->ref.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6637 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 4b147936fa509650beaf638b331573c23ba4d609 , < 381f543ed35c434d5b707369aa5dcd69ecf440af (git)
Affected: 4b147936fa509650beaf638b331573c23ba4d609 , < 4472579bd1c83708b6fe623c870cdf728e947205 (git)
Affected: 4b147936fa509650beaf638b331573c23ba4d609 , < 23b4106e8b35823acc79e206c7745f55b9cfd78b (git)
Affected: 4b147936fa509650beaf638b331573c23ba4d609 , < 06e816bed499fe47f39f12044382cc5d064485fb (git)
Affected: 4b147936fa509650beaf638b331573c23ba4d609 , < 5597bb8db6855fcb97a67196d227fea359bcd81c (git)
Affected: 4b147936fa509650beaf638b331573c23ba4d609 , < cf4e31d5da80fae4c9cdbe7af55b7c3ad213f0e4 (git)
Affected: 4b147936fa509650beaf638b331573c23ba4d609 , < 3403d9bb27ebc3572bd048620746b4414e073bf9 (git)
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Linux Linux Affected: 4.17
Unaffected: 0 , < 4.17 (semver)
Unaffected: 6.1.191 , ≤ 6.1.* (semver)
Unaffected: 6.6.161 , ≤ 6.6.* (semver)
Unaffected: 6.12.115 , ≤ 6.12.* (semver)
Unaffected: 6.18.60 , ≤ 6.18.* (semver)
Unaffected: 7.2.14 , ≤ 7.2.* (semver)
Unaffected: 7.3.1 , ≤ 7.3.* (semver)
Unaffected: 7.4-rc1 , ≤ * (original_commit_for_fix)
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{
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    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/trace_events_hist.c",
            "kernel/trace/trace_events_synth.c",
            "kernel/trace/trace_synth.h"
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          "versions": [
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              "version": "4b147936fa509650beaf638b331573c23ba4d609",
              "versionType": "git"
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              "versionType": "git"
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              "versionType": "semver"
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              "version": "6.6.161",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.115",
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            {
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              "status": "unaffected",
              "version": "7.3.1",
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            {
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              "version": "7.4-rc1",
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      "cpeApplicability": [
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                  "versionEndExcluding": "6.1.191",
                  "versionStartIncluding": "4.17",
                  "vulnerable": true
                },
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              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing/histograms: Verify event_call identity when updating synth_event refcount\n\nIn event_hist_trigger_parse() and hist_unreg_all(), the histogram\nregistration and unregistration paths look up find_synth_event() using\ntrace_event_name(file-\u003eevent_call) and adjust se-\u003eref if a match is\nfound.\n\nBecause find_synth_event() only compares the event basename, registering\nor removing a histogram on a non-synthetic trace event whose basename\nmatches a synthetic event erroneously modifies the synthetic event\u0027s\nreference count.  If a histogram is registered on the non-synthetic\nevent before the synthetic event is created and removed afterwards,\nse-\u003eref is decremented without a matching increment, allowing the\nsynthetic event to be freed while an active histogram action still holds\na pointer to it.\n\nIntroduce find_synth_event_call() to verify that \u0026se-\u003ecall matches\nfile-\u003eevent_call before adjusting se-\u003eref."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "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"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The colliding basename is supplied by local writes: event_trigger_write() \u2192 trigger_process_regex() \u2192 event_hist_trigger_parse()/hist_unreg_all() on events/\u003csystem\u003e/\u003cevent\u003e/trigger, and synth_events_write() \u2192 create_or_delete_synth_event() on synthetic_events. No network protocol carries this input.\nAC:L - The attacker drives a fully ordered sequence: a hist on a non-synth event (no se-\u003eref++), then a same-basename synth event, then an ACTION_TRACE hist that stores data-\u003esynth_event and increments se-\u003eref, then the !hist/hist_unreg_all path which decrements se-\u003eref, then synth_event_delete(). event_mutex serializes it; no victim-owned state is required.\nPR:L - event_trigger_open() and synth_events_open() only call security_locked_down(LOCKDOWN_TRACEFS); both files are TRACE_MODE_WRITE (0640) with no capable() check. tracefs_parse_param() accepts uid=/gid= and tracefs_apply_options() applies that owner, so a delegated tracing user can write them; tracefs has no FS_USERNS_MOUNT.\nUI:N - The attacker writes the hist commands, creates and deletes the colliding synth event via synth_events_write(), and can fire the leftover ACTION_TRACE histogram from their own process (any syscall that hits the remaining event). No separate victim action is required.\nS:U - destroy_synth_event() kfree\u0027s struct synth_event while action_trace() still holds data-\u003esynth_event; that UAF is confined to the host tracing heap and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - Once free_synth_event() has kfree\u0027d the object, action_trace() still reads data-\u003esynth_event and trace_synth() follows event-\u003etp and tp-\u003efuncs; reclaiming that kmalloc object lets the attacker control those reads, giving a kernel-memory disclosure primitive.\nI:H - trace_synth() calls probe_func taken from the dangling event-\u003etp-\u003efuncs, and a later action_data_destroy() does data-\u003esynth_event-\u003eref-- on the freed object; spraying the reclaimed synth_event therefore yields a function-pointer hijack and a write primitive.\nA:H - trace_synth() does static_key_enabled(\u0026tp-\u003ekey) on event-\u003etp from the freed synth_event the first time the leftover histogram fires, which oopses on a poisoned or unmapped pointer; the UAF is repeatable at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-11-03T19:13:02.404Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/381f543ed35c434d5b707369aa5dcd69ecf440af"
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          "url": "https://git.kernel.org/stable/c/4472579bd1c83708b6fe623c870cdf728e947205"
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          "url": "https://git.kernel.org/stable/c/23b4106e8b35823acc79e206c7745f55b9cfd78b"
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          "url": "https://git.kernel.org/stable/c/06e816bed499fe47f39f12044382cc5d064485fb"
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        {
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      "title": "tracing/histograms: Verify event_call identity when updating synth_event refcount",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-99233",
    "datePublished": "2026-11-02T16:06:40.643Z",
    "dateReserved": "2026-09-25T10:25:14.402Z",
    "dateUpdated": "2026-11-03T19:13:02.404Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
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      "date": "2026-11-04",
      "epss": "0.00121",
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                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "kernel/trace/trace_events_hist.c",
                  "kernel/trace/trace_events_synth.c",
                  "kernel/trace/trace_synth.h"
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                "defaultStatus": "affected",
                "product": "Linux",
                "programFiles": [
                  "kernel/trace/trace_events_hist.c",
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                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
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          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing/histograms: Verify event_call identity when updating synth_event refcount\n\nIn event_hist_trigger_parse() and hist_unreg_all(), the histogram\nregistration and unregistration paths look up find_synth_event() using\ntrace_event_name(file-\u003eevent_call) and adjust se-\u003eref if a match is\nfound.\n\nBecause find_synth_event() only compares the event basename, registering\nor removing a histogram on a non-synthetic trace event whose basename\nmatches a synthetic event erroneously modifies the synthetic event\u0027s\nreference count.  If a histogram is registered on the non-synthetic\nevent before the synthetic event is created and removed afterwards,\nse-\u003eref is decremented without a matching increment, allowing the\nsynthetic event to be freed while an active histogram action still holds\na pointer to it.\n\nIntroduce find_synth_event_call() to verify that \u0026se-\u003ecall matches\nfile-\u003eevent_call before adjusting se-\u003eref."
          }
        ],
        "id": "CVE-2026-99233",
        "lastModified": "2026-11-03T20:18:29.270",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-11-02T16:17:48.390",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/06e816bed499fe47f39f12044382cc5d064485fb"
          },
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/23b4106e8b35823acc79e206c7745f55b9cfd78b"
          },
          {
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            "url": "https://git.kernel.org/stable/c/3403d9bb27ebc3572bd048620746b4414e073bf9"
          },
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            "url": "https://git.kernel.org/stable/c/381f543ed35c434d5b707369aa5dcd69ecf440af"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/4472579bd1c83708b6fe623c870cdf728e947205"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/5597bb8db6855fcb97a67196d227fea359bcd81c"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/cf4e31d5da80fae4c9cdbe7af55b7c3ad213f0e4"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-11-05T00:20:33+00:00",
      "cve": "CVE-2026-99233",
      "id": "CVE-2026-99233",
      "initial_release_date": "2026-11-02T16:06:40.643000+00:00",
      "product_status:known_affected": "162",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: kernel: Privilege escalation via use-after-free in tracing subsystem",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-99233.json",
      "version": "3"
    }
  }
}



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  • 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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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