CVE-2026-74493 (GCVE-0-2026-74493)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:27 – Updated: 2026-08-17 05:47
VLAI
Title
net/smc: fix socket use-after-free during link group termination
Summary
In the Linux kernel, the following vulnerability has been resolved: net/smc: fix socket use-after-free during link group termination __smc_lgr_terminate() drops conns_lock after finding a connection in lgr->conns_all, but before taking a reference on its socket. The connection is embedded in the socket, and its registration reference protects it only while the connection remains in the tree. A concurrent close can unregister the connection and drop that reference, freeing the socket before the termination worker reaches sock_hold(). The race is reachable when close overlaps link group termination. Local stress testing reproduced the use-after-free and KASAN reported: BUG: KASAN: slab-use-after-free in __smc_lgr_terminate.part.0 [smc] Write of size 4 by task kworker/3:3 Workqueue: events smc_lgr_terminate_work [smc] __smc_lgr_terminate.part.0 [smc] The socket was allocated by smc_create(), freed through slab_free_after_rcu_debug(), and was followed by: refcount_t: addition on 0; use-after-free. __smc_lgr_terminate.part.0 [smc] Take the socket reference while conns_lock still protects the tree entry. The unregister path then cannot drop the last reference until termination has finished using the socket.
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: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 , < 5a42f162b857019a4c10ff687dc3bcdf51831865 (git)
Affected: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 , < 281c103a8eaed59001ce952f231df1b07674215a (git)
Affected: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 , < f807a63d0d95680c34f677700da9148a07d7c78f (git)
Affected: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 , < f0541a775d04c88e90ba448e35ce0d743512822a (git)
Affected: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 , < f621d6ebeebb6374342571e4ddf45fdbc420f6cd (git)
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Linux Linux Affected: 5.5
Unaffected: 0 , < 5.5 (semver)
Unaffected: 6.6.151 , ≤ 6.6.* (semver)
Unaffected: 6.12.103 , ≤ 6.12.* (semver)
Unaffected: 6.18.44 , ≤ 6.18.* (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
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              "status": "unaffected",
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              "versionType": "original_commit_for_fix"
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix socket use-after-free during link group termination\n\n__smc_lgr_terminate() drops conns_lock after finding a connection in\nlgr-\u003econns_all, but before taking a reference on its socket. The connection\nis embedded in the socket, and its registration reference protects it only\nwhile the connection remains in the tree.\n\nA concurrent close can unregister the connection and drop that reference,\nfreeing the socket before the termination worker reaches sock_hold().\n\nThe race is reachable when close overlaps link group termination.\nLocal stress testing reproduced the use-after-free and KASAN reported:\n\n  BUG: KASAN: slab-use-after-free in __smc_lgr_terminate.part.0 [smc]\n  Write of size 4 by task kworker/3:3\n  Workqueue: events smc_lgr_terminate_work [smc]\n  __smc_lgr_terminate.part.0 [smc]\n\nThe socket was allocated by smc_create(), freed through\nslab_free_after_rcu_debug(), and was followed by:\n\n  refcount_t: addition on 0; use-after-free.\n  __smc_lgr_terminate.part.0 [smc]\n\nTake the socket reference while conns_lock still protects the tree entry.\nThe unregister path then cannot drop the last reference until termination\nhas finished using the socket."
        }
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            "version": "3.1"
          },
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              "value": "AV:N - The bug is hit in __smc_lgr_terminate() when a link group shuts down; that path is driven by SMC LLC control messages from a remote peer over RoCE/RDMA (smc_llc_rx_handler), including DELETE_LINK_ALL and protocol-violation termination, not only local syscalls.\nAC:L - An SMC peer can overlap link-group termination with connection teardown by sending DELETE_LINK_ALL (or a terminating LLC event) while aborting/closing the same session; the fix report shows reliable stress reproduction, and the attacker controls both sides of the terminate/close race.\nPR:N - Exploitation needs only completing an SMC handshake as a network peer to the victim; no local account, capabilities, or namespace admin rights on the victim host are required beyond normal remote connectivity to the SMC service.\nUI:N - No victim user action is needed; a remote peer can trigger termination and concurrent connection teardown purely through kernel protocol handling, without the user mounting filesystems, opening files, or performing other interactive steps.\nS:U - The impact stays within the host kernel boundary (memory corruption and potential local privilege escalation) and does not cross VM, container, or IOMMU security authorities into another trust domain.\nC:H - KASAN reported slab-use-after-free in __smc_lgr_terminate with refcount_t addition on 0 during sock_hold() on a freed smc_sock; UAF on kernel heap objects can be turned into arbitrary kernel memory disclosure via heap grooming.\nI:H - The UAF is a write of size 4 to freed socket memory during sock_hold(), giving a kernel heap corruption primitive that can be developed into arbitrary write or control-flow hijack for kernel code execution.\nA:H - The reported UAF occurs in the smc_lgr_terminate workqueue and can crash the kernel (oops/panic); repeated remote triggering against SMC/RoCE services can also cause sustained denial of service."
            }
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        "shortName": "Linux"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74493",
    "datePublished": "2026-08-15T12:27:21.980Z",
    "dateReserved": "2026-08-15T05:44:03.906Z",
    "dateUpdated": "2026-08-17T05:47:49.546Z",
    "state": "PUBLISHED"
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    "suse_vex": {
      "aggregate_severity": "critical",
      "current_release_date": "2026-08-17T16:26:21Z",
      "cve": "CVE-2026-74493",
      "id": "CVE-2026-74493",
      "initial_release_date": "2026-08-15T23:51:41Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-74493",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-74493.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.