CVE-2025-37776 (GCVE-0-2025-37776)

Vulnerability from cvelistv5 – Published: 2025-05-01 13:07 – Updated: 2026-08-05 11:57
VLAI
Title
ksmbd: fix use-after-free in smb_break_all_levII_oplock()
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in smb_break_all_levII_oplock() There is a room in smb_break_all_levII_oplock that can cause racy issues when unlocking in the middle of the loop. This patch use read lock to protect whole loop.
Severity
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < 296cb5457cc6f4a754c4ae29855f8a253d52bcc6 (git)
Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < d54ab1520d43e95f9b2e22d7a05fc9614192e5a5 (git)
Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < d73686367ad68534257cd88a36ca3c52cb8b81d8 (git)
Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < 18b4fac5ef17f77fed9417d22210ceafd6525fc7 (git)
Create a notification for this product.
Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.6.88 , ≤ 6.6.* (semver)
Unaffected: 6.12.25 , ≤ 6.12.* (semver)
Unaffected: 6.14.4 , ≤ 6.14.* (semver)
Unaffected: 6.15 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Show details on NVD website
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{
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          "product": "Linux",
          "programFiles": [
            "fs/smb/server/oplock.c",
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free in smb_break_all_levII_oplock()\n\nThere is a room in smb_break_all_levII_oplock that can cause racy issues\nwhen unlocking in the middle of the loop. This patch use read lock\nto protect whole loop."
        }
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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              "lang": "en",
              "value": "AV:N - ksmbd is the in-kernel SMB server on TCP/445, and every trigger path (SMB2 WRITE, CREATE with O_TRUNC, SET_INFO alloc-size/rename, IOCTL copychunk/zero-data, LOCK) is driven entirely by remote SMB2 traffic. No local access is required.\nAC:L - The attacker controls both sides of the race: one connection holds the level-II oplock and simply withholds the SMB2_OPLOCK_BREAK ack, pinning the RCU-unlocked window open for up to OPLOCK_WAIT_TIME (35 s), while other connections close handles on the same inode to drive opinfo_del()/opinfo_put(). An attacker-created race with a multi-second window is reliably winnable and repeatable.\nPR:L - All call sites dereference work-\u003etcon-\u003eshare_conf, so a completed SESSION_SETUP and TREE_CONNECT are needed \u2014 any unprivileged share account (including guest where \"map to guest\" is configured) suffices, with no administrative rights. This matches the sibling post-authentication ksmbd UAFs.\nUI:N - The attacker drives every step from its own SMB connections \u2014 taking the oplock, stalling the break ack, and closing handles concurrently. No action by an administrator or any other client is needed.\nS:U - The freed object and the resulting corruption are both inside the kernel\u0027s own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The ~176-byte oplock_info lives in the general kmalloc-192 cache and is remotely sprayable, so the freed object can be reclaimed with attacker-controlled bytes at the op_entry.next offset, yielding a chosen brk_op whose -\u003econn and -\u003eo_lease-\u003estate dereferences give arbitrary kernel memory disclosure.\nI:H - With a controlled brk_op pointer, atomic_inc_not_zero(\u0026brk_op-\u003erefcount) is an arbitrary-address increment write, and oplock_break() then manipulates wait-queue lists and queues work off the fake object \u2014 a use-after-free that is exploitable for control-flow hijack and arbitrary kernel code execution.\nA:H - Even unweaponized, following op_entry.next out of a freed oplock_info dereferences freed/poisoned memory and reliably oopses or panics the kernel, and the attacker can repeat the sequence to keep the SMB server down."
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    "datePublished": "2025-05-01T13:07:14.998Z",
    "dateReserved": "2025-04-16T04:51:23.939Z",
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      "product_status:known_affected": "2",
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      "source": "Microsoft CSAF VEX",
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      "title": "ksmbd: fix use-after-free in smb_break_all_levII_oplock()",
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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-06-30T10:24:26+00:00",
      "cve": "CVE-2025-37776",
      "id": "CVE-2025-37776",
      "initial_release_date": "2025-05-01T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ksmbd: fix use-after-free in smb_break_all_levII_oplock()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-37776.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.