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CVE-2026-74436 (GCVE-0-2026-74436)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:59 – Updated: 2026-08-23 12:47
VLAI
Title
rxrpc: serialize kernel accept preallocation with socket teardown
Summary
In the Linux kernel, the following vulnerability has been resolved: rxrpc: serialize kernel accept preallocation with socket teardown rxrpc_kernel_charge_accept() reads rx->backlog without any socket/backlog synchronization and passes that raw pointer into rxrpc_service_prealloc_one(). A concurrent rxrpc_discard_prealloc() sets rx->backlog = NULL and frees the backlog rings, so a kernel preallocation worker can keep using a freed struct rxrpc_backlog while updating *_backlog_head/tail and array slots. Serialize the state check and backlog lookup with the socket lock, and reject kernel preallocation once teardown has disabled listening or discarded the service backlog.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 , < d6207326b4ca0ae1041281b6af9df53f8080669a (git)
Affected: 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 , < 11b429b84c87cb5a0152f14e7d6cb649ed363901 (git)
Affected: 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 , < c20d983968f239574290cf804a58cde18ad1c559 (git)
Affected: 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 , < 0337cdba0c477f176c0459bed012109453184573 (git)
Affected: 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 , < dfa0b2bbc5e50119f89c6b5407faa5ed86dfa7c5 (git)
Affected: 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 , < 35a967ff8b24db09ee429c39c5b5e6571639997d (git)
Affected: 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 , < 1741378a7a83dfd8e53a9196730df709b903cd33 (git)
Affected: 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 , < dc175389b18c29a5303ee83169ec653adfae3e17 (git)
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Linux Linux Affected: 4.9
Unaffected: 0 , < 4.9 (semver)
Unaffected: 5.10.266 , ≤ 5.10.* (semver)
Unaffected: 5.15.217 , ≤ 5.15.* (semver)
Unaffected: 6.1.184 , ≤ 6.1.* (semver)
Unaffected: 6.6.148 , ≤ 6.6.* (semver)
Unaffected: 6.12.101 , ≤ 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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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc: serialize kernel accept preallocation with socket teardown\n\nrxrpc_kernel_charge_accept() reads rx-\u003ebacklog without any\nsocket/backlog synchronization and passes that raw pointer into\nrxrpc_service_prealloc_one(). A concurrent rxrpc_discard_prealloc()\nsets rx-\u003ebacklog = NULL and frees the backlog rings, so a kernel\npreallocation worker can keep using a freed struct rxrpc_backlog\nwhile updating *_backlog_head/tail and array slots.\n\nSerialize the state check and backlog lookup with the socket lock,\nand reject kernel preallocation once teardown has disabled\nlistening or discarded the service backlog."
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              "value": "AV:N - RxRPC is a UDP network protocol; remote peers can send packets to AFS callback-manager listeners (port 7001) that instantiate incoming calls and queue kernel preallocation work reaching rxrpc_kernel_charge_accept().\nAC:L - The attacker controls the preallocation side by flooding concurrent rxrpc/AFS callback traffic while a peer thread tears down the same socket via listen(0), shutdown, or close during AFS netns exit, creating a winnable race.\nPR:N - No local account, capability, or authentication is required to reach the vulnerable preallocation path; any remote host that can deliver rxrpc/UDP packets to a listening AFS callback manager can drive the charge_accept worker.\nUI:N - Exploitation requires no victim interaction beyond normal background AFS service operation; the attacker triggers the bug purely through network traffic timed against automatic or administrative socket teardown.\nS:U - The use-after-free corrupts kernel heap metadata and rxrpc backlog structures within kernel memory, enabling local privilege escalation but not crossing a VM, container, or IOMMU security boundary by itself.\nC:H - Concurrent use of a freed struct rxrpc_backlog allows reads and corruption of recycled slab memory, providing a standard kmalloc UAF primitive that can leak kernel pointers and sensitive data.\nI:H - The race writes peer, connection, and call pointers plus head/tail indices into freed backlog ring slots, enabling heap grooming and arbitrary kernel memory corruption exploitable for code execution.\nA:H - Use-after-free on the backlog structure during concurrent head/tail and pointer-array updates can cause kernel oops, panic, or hang, and repeated triggering enables sustained denial of service."
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-20T23:28:44+00:00",
      "cve": "CVE-2026-74436",
      "id": "CVE-2026-74436",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: rxrpc: serialize kernel accept preallocation with socket teardown",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74436.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.