CVE-2026-89634 (GCVE-0-2026-89634)
Vulnerability from cvelistv5
Published
2026-09-11 19:45
Modified
2026-10-19 08:50
Severity ?
9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix ALIGN() overflow in symlink_data() error context loop The check added by commit 7d9a7f1f96cd ("smb/client: fix possible infinite loop and oob read in symlink_data()") compared the post-ALIGN length against the remaining buffer, but ALIGN() itself can overflow: for ErrorDataLength near UINT32_MAX (e.g. 0xFFFFFFF9), ALIGN(x, 8) wraps to 0, so the subsequent bounds check passes, and the loop advances by zero bytes leaving 'p' pointing into stale data. Fix by checking the raw ErrorDataLength against the remaining space before applying ALIGN(), then checking again after. Since raw_len is bounded by the buffer, raw_len + 7 cannot overflow, so the second check is an exact post-alignment bounds guard.
References
Impacted products
Vendor Product Version
Linux Linux Version: 76894f3e2f71177747b8b4763fb180e800279585
Version: 76894f3e2f71177747b8b4763fb180e800279585
Version: 76894f3e2f71177747b8b4763fb180e800279585
Version: 76894f3e2f71177747b8b4763fb180e800279585
Version: 76894f3e2f71177747b8b4763fb180e800279585
Version: 76894f3e2f71177747b8b4763fb180e800279585
Version: 2d046892a493d9760c35fdaefc3017f27f91b621
Version: 6.0.16   ≤
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{
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/smb2file.c"
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            },
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              "status": "unaffected",
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            },
            {
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            {
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              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.188",
                  "versionStartIncluding": "6.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.157",
                  "versionStartIncluding": "6.1",
                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix ALIGN() overflow in symlink_data() error context loop\n\nThe check added by commit 7d9a7f1f96cd (\"smb/client: fix possible\ninfinite loop and oob read in symlink_data()\") compared the post-ALIGN\nlength against the remaining buffer, but ALIGN() itself can overflow:\nfor ErrorDataLength near UINT32_MAX (e.g. 0xFFFFFFF9), ALIGN(x, 8)\nwraps to 0, so the subsequent bounds check passes, and the loop\nadvances by zero bytes leaving \u0027p\u0027 pointing into stale data.\n\nFix by checking the raw ErrorDataLength against the remaining space\nbefore applying ALIGN(), then checking again after.  Since raw_len is\nbounded by the buffer, raw_len + 7 cannot overflow, so the second check\nis an exact post-alignment bounds guard."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.1,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The flaw is in the SMB client parser of a STATUS_STOPPED_ON_SYMLINK CREATE error returned over TCP/445; a malicious, compromised, or MITM SMB server supplies the crafted ErrorDataLength in the network response.\nAC:L - The attacker fully controls ErrorContextCount, ErrorId, and ErrorDataLength in a single SMB2 error response; setting ErrorDataLength near UINT32_MAX (e.g. 0xFFFFFFF9) makes ALIGN() wrap to 0 and bypasses the bounds check with no race or attacker-uncontrolled condition.\nPR:N - The attacker is the remote SMB peer and needs no account or capability on the victim client; guest/null sessions and already-established mounts are enough for the client to parse the malformed error.\nUI:N - Persistent fstab, autofs, and systemd automounts plus reconnect-driven path walks already open/lookup files on the share, so a compromised or MITM\u0027d server can return the crafted symlink error during ordinary client activity with no extra user action.\nS:U - Impact stays in the client kernel SMB parser and its memory; this is not a VM escape, IOMMU bypass, or cross-scope sandbox escape.\nC:H - The ALIGN overflow bypasses the ErrorDataLength bounds check added to stop out-of-bounds reads in this loop (CVE-2026-52967/CVE-2026-31613); a stale overlapping context pointer can then be parsed as symlink PathBuffer data and UTF-16-decoded into a userspace target.\nI:N - The defect only mis-advances a read-side parser pointer after ALIGN() wraps to 0; it does not write out of bounds or provide a kernel memory-modification primitive.\nA:H - With the skip length wrapped to 0 the error-context loop fails to consume the declared payload and can stall or walk a stale pointer; that is the remaining hole in the 32-bit infinite-loop/OOB class in this function and can hang or oops the client kernel."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:50:06.331Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/2b4a25baa0b936fef6915c0459925077b324ecaf"
        },
        {
          "url": "https://git.kernel.org/stable/c/b89d678f9eafcf8d74885983166ba26b40a04ea0"
        },
        {
          "url": "https://git.kernel.org/stable/c/657372ba6ea50b4474d2a6a610097eae8cd1f3e9"
        },
        {
          "url": "https://git.kernel.org/stable/c/1f824f61d1df52392eaf0b74dfa5659d724fde30"
        },
        {
          "url": "https://git.kernel.org/stable/c/62a3025983c8c735a3c6fc85a59316f31b59af07"
        },
        {
          "url": "https://git.kernel.org/stable/c/62656b024efc21c3230eade1a847f25871c3d2bb"
        }
      ],
      "title": "smb: client: fix ALIGN() overflow in symlink_data() error context loop",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89634",
    "datePublished": "2026-09-11T19:45:28.823Z",
    "dateReserved": "2026-09-11T19:38:34.739Z",
    "dateUpdated": "2026-10-19T08:50:06.331Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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