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CVE-2026-74262 (GCVE-0-2026-74262)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:57 – Updated: 2026-08-17 05:45
VLAI
Title
kcm: use WRITE_ONCE() when changing lower socket callbacks
Summary
In the Linux kernel, the following vulnerability has been resolved: kcm: use WRITE_ONCE() when changing lower socket callbacks kcm_attach() replaces a live lower TCP socket's sk_data_ready and sk_write_space callbacks with KCM handlers, and kcm_unattach() restores them later. Those callback-pointer updates are still plain stores even though the same fields can be read and invoked concurrently on other CPUs. If another CPU observes an older callback snapshot after the live field has already been restored, callback execution can run with a mismatched target and sk_user_data state, leading to stale or misdirected wakeups. Use WRITE_ONCE() for the callback replacement and restore operations so these shared callback fields follow the same visibility contract already established by the earlier 4022 fixes.
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: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3 , < 0cb3e2f40679032c1aa2186280a86e5ead0161ee (git)
Affected: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3 , < fa26e4606aed0f7fe793c325506adeda1d847a43 (git)
Affected: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3 , < b4ccd6eef671d7c44a30123cd29f3acf3de8468e (git)
Affected: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3 , < b8c90823cdfb5f3d22f261aeb3e9066612853c36 (git)
Affected: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3 , < 11faefd11ce2448bac7279ab302dd1954a6547fe (git)
Affected: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3 , < f01fb6138f8eb606b56ce9158e2d8b72352c53f4 (git)
Affected: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3 , < 9684fff87124b201e11dea01ded9173025359a0f (git)
Affected: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3 , < 47186409c092cd7dd70350999186c700233e854d (git)
guessed Create a notification for this product.
Linux Linux Affected: 4.6
Unaffected: 0 , < 4.6 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 5.15.212 , ≤ 5.15.* (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nkcm: use WRITE_ONCE() when changing lower socket callbacks\n\nkcm_attach() replaces a live lower TCP socket\u0027s sk_data_ready and\nsk_write_space callbacks with KCM handlers, and kcm_unattach() restores\nthem later. Those callback-pointer updates are still plain stores even\nthough the same fields can be read and invoked concurrently on other\nCPUs.\n\nIf another CPU observes an older callback snapshot after the live field\nhas already been restored, callback execution can run with a mismatched\ntarget and sk_user_data state, leading to stale or misdirected wakeups.\n\nUse WRITE_ONCE() for the callback replacement and restore operations so\nthese shared callback fields follow the same visibility contract already\nestablished by the earlier 4022 fixes."
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              "lang": "en",
              "value": "AV:L - The bug is in kcm_attach()/kcm_unattach() callback replacement reachable only via local socket()/ioctl(SIOCKCMATTACH/UNATTACH); remote TCP can trigger callback invocation but cannot perform attach/detach without local access to the KCM socket.\nAC:L - The attacker controls both sides of the race by concurrently issuing attach/unattach ioctls while driving RX/TX on the same TCP socket to provoke READ_ONCE(sk_data_ready/sk_write_space) on other CPUs during callback pointer transitions.\nPR:L - No capability checks exist in KCM; any local user who can create AF_KCM sockets and load a BPF_PROG_TYPE_SOCKET_FILTER program (allowed without CAP_BPF on many systems, or via user-namespace capabilities) can reach the vulnerable ioctl path.\nUI:N - Exploitation requires only attacker-controlled local socket operations and concurrent network I/O; no victim user or administrator action is needed beyond the attacker using their own sockets.\nS:U - Impact is kernel memory corruption and privilege escalation within the same security authority; this is not a cross-boundary escape such as guest-to-host VM breakout or IOMMU bypass.\nC:H - Plain stores to sk_data_ready/sk_write_space can desynchronize from sk_user_data, letting stale KCM callbacks dereference freed or mismatched kcm_psock/strparser state and leak attacker-influenced kernel heap contents.\nI:H - Misdirected psock_write_space/psock_data_ready on dangling kcm_psock can corrupt heap metadata and queue_work on freed kcm_sock objects, enabling control-flow hijack and arbitrary kernel write primitives.\nA:H - The data race causes use-after-free and invalid pointer dereferences in softirq/workqueue callback paths, producing reliable kernel oops/panic or hang even when full exploitation is not achieved."
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    "dateUpdated": "2026-08-17T05:45:10.909Z",
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Those callback-pointer updates are still plain stores even\\nthough the same fields can be read and invoked concurrently on other\\nCPUs.\\n\\nIf another CPU observes an older callback snapshot after the live field\\nhas already been restored, callback execution can run with a mismatched\\ntarget and sk_user_data state, leading to stale or misdirected wakeups.\\n\\nUse WRITE_ONCE() for the callback replacement and restore operations so\\nthese shared callback fields follow the same visibility contract already\\nestablished by the earlier 4022 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-19T13:21:39+00:00",
      "cve": "CVE-2026-74262",
      "id": "CVE-2026-74262",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: kcm: use WRITE_ONCE() when changing lower socket callbacks",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74262.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.