CVE-2026-43185 (GCVE-0-2026-43185)

Vulnerability from cvelistv5 – Published: 2026-05-06 11:27 – Updated: 2026-08-05 12:26
VLAI
Title
ksmbd: fix signededness bug in smb_direct_prepare_negotiation()
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix signededness bug in smb_direct_prepare_negotiation() smb_direct_prepare_negotiation() casts an unsigned __u32 value from sp->max_recv_size and req->preferred_send_size to a signed int before computing min_t(int, ...). A maliciously provided preferred_send_size of 0x80000000 will return as smaller than max_recv_size, and then be used to set the maximum allowed alowed receive size for the next message. By sending a second message with a large value (>1420 bytes) the attacker can then achieve a heap buffer overflow. This fix replaces min_t(int, ...) with min_t(u32)
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: 0626e6641f6b467447c81dd7678a69c66f7746cf , < ceae058eb707ddd0d68f0872f9d9f23b7c30c37b (git)
Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < 55abc475d096da4a5356b6efb0cfdc6156bc1550 (git)
Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < 6b4f875aac344cdd52a1f34cc70ed2f874a65757 (git)
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Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.18.16 , ≤ 6.18.* (semver)
Unaffected: 6.19.6 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
            "fs/smb/server/transport_rdma.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix signededness bug in smb_direct_prepare_negotiation()\n\nsmb_direct_prepare_negotiation() casts an unsigned __u32 value\nfrom sp-\u003emax_recv_size and req-\u003epreferred_send_size to a signed\nint before computing min_t(int, ...). A maliciously provided\npreferred_send_size of 0x80000000 will return as smaller than\nmax_recv_size, and then be used to set the maximum allowed\nalowed receive size for the next message.\n\nBy sending a second message with a large value (\u003e1420 bytes)\nthe attacker can then achieve a heap buffer overflow.\n\nThis fix replaces min_t(int, ...) with min_t(u32)"
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              "value": "AV:N - The vulnerable ksmbd SMB Direct negotiation is reached by a remote peer over the network via the RDMA listener on SMB Direct ports such as 445/5445.\nAC:L - An attacker can trigger the bug with a crafted negotiation request followed by an oversized data-transfer message; no race or victim-controlled timing is required.\nPR:N - The vulnerable path runs during SMB Direct transport negotiation before SMB authentication or session setup, so no credentials or prior privileges are required.\nUI:N - No victim user action is needed beyond the server exposing ksmbd SMB Direct; the attacker sends network protocol messages directly.\nS:U - The impact is kernel memory corruption within the same host security authority, not a cross-scope escape such as guest-to-host or IOMMU boundary bypass.\nC:H - The signedness bug lets the attacker turn a small allocated receive buffer into a huge posted RDMA receive target, causing attacker-controlled kernel heap memory corruption that can plausibly be leveraged for information disclosure.\nI:H - The second SMB Direct message causes an out-of-bounds write/DMA overwrite into kernel heap memory, which is high-integrity impact and plausibly exploitable for control-flow or data corruption.\nA:H - The heap buffer overflow is remotely triggerable pre-authentication and can crash or panic the kernel even without full code execution."
            }
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43185",
    "datePublished": "2026-05-06T11:27:56.386Z",
    "dateReserved": "2026-05-01T14:12:55.991Z",
    "dateUpdated": "2026-08-05T12:26:23.248Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "version": "5"
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    "redhat_vex": {
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      "id": "CVE-2026-43185",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ksmbd: fix signededness bug in smb_direct_prepare_negotiation()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43185.json",
      "version": "3"
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  }
}



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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.


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