CVE-2026-31539 (GCVE-0-2026-31539)

Vulnerability from cvelistv5 – Published: 2026-04-24 14:30 – Updated: 2026-08-05 12:23
VLAI
Title
smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available The logic off managing recv credits by counting posted recv_io and granted credits is racy. That's because the peer might already consumed a credit, but between receiving the incoming recv at the hardware and processing the completion in the 'recv_done' functions we likely have a window where we grant credits, which don't really exist. So we better have a decicated counter for the available credits, which will be incremented when we posted new recv buffers and drained when we grant the credits to the peer.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 5fb9b459b3686e366640edd4e62805ef7b4de927 , < e811e60e1cc79923c4388146eb1fa26a7482731e (git)
Affected: 5fb9b459b3686e366640edd4e62805ef7b4de927 , < f99996870222b598914a1f49d7375dc23752c237 (git)
Affected: 5fb9b459b3686e366640edd4e62805ef7b4de927 , < 6e3c5052f9686192e178806e017b7377155f4bab (git)
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Linux Linux Affected: 6.18
Unaffected: 0 , < 6.18 (semver)
Unaffected: 6.18.11 , ≤ 6.18.* (semver)
Unaffected: 6.19.1 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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              "value": "AV:N - SMBDirect is reached by a remote RDMA peer through RDMA CM listeners on SMBDirect/SMB ports such as 5445 and 445. The ksmbd server path processes the affected negotiation and data-transfer credit handling from network-originated RDMA messages.\nAC:L - The issue is a receive-credit accounting race, but the remote peer can repeatedly drive both message arrival and credit-request/response behavior with crafted SMBDirect traffic. No unusual victim state or uncontrollable condition is required beyond an enabled SMBDirect RDMA deployment.\nPR:N - The server-side path accepts the RDMA connection and performs SMBDirect negotiation and data-transfer credit handling before SMB session authentication. A remote peer does not need SMB credentials to reach the vulnerable credit logic.\nUI:N - Exploitation against the server path requires only network/RDMA traffic from the attacker. No local user or administrator action is needed after the service is exposed.\nS:U - The impact remains within the kernel SMBDirect/SMB service security authority. There is no VM escape, IOMMU bypass, or cross-authority boundary crossing.\nC:N - The bug overgrants receive credits but does not expose a kernel read primitive; incoming payload bounds are checked before reassembly. An RDMA send without a posted receive should produce transport/RNR failure rather than disclose memory.\nI:N - The investigation did not identify an arbitrary write or memory-corruption primitive. The false credit causes receive-queue/transport state inconsistency, not attacker-controlled modification of kernel data.\nA:H - False credits can allow the peer to send when no real receive buffer is posted, causing RDMA QP/transport errors and SMBDirect disconnects with RNR retries disabled. Because this is remotely and unauthenticatedly repeatable against the exposed SMBDirect service, availability impact is high."
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      "cve": "CVE-2026-31539",
      "id": "CVE-2026-31539",
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      "title": "SUSE CVE CVE-2026-31539",
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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

Author Source Type Date Other

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.