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CVE-2026-64257

Critical Vulnerability: CVE-2026-64257 — linux — linux_kernel

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject overlapping data areas in SMB2 responses Commit 53b7c271f06b ("smb: client: restrict implied bcc[0] exemption to responses without data area") restricted the implied bcc[0] length exception to responses without a data area. However, the overlap handling in __smb2_calc_size() clears data_length, which can make an invalid response appear to have no data area and so qualify for the exception. Track data area

Wednesday, August 12, 2026linuxVulnios Threat Intelligence
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Vulnerability Snapshot

CVE-2026-64257 is rated CRITICAL — exploitation is trivial or already observed in the wild and impact is severe. Patch immediately, not on the next maintenance window.

Affected technology: linux_kernel.

Executive Summary

In the Linux kernel, the following vulnerability has been resolved:

smb: client: reject overlapping data areas in SMB2 responses

Commit 53b7c271f06b ("smb: client: restrict implied bcc[0] exemption to

responses without data area") restricted the implied bcc[0] length

exception to responses without a data area. However, the overlap

handling in __smb2_calc_size() clears data_length, which can make an

invalid response appear to have no data area and so qualify for the

exception.

Track data area overlap separately and reject such responses before

applying the length compatibility exceptions.

Why It Matters

CVE-2026-64257 is rated CRITICAL severity, requiring immediate attention from security teams.

CVSS Base Score: 9.1/10

Affected Technologies

Vendors: linux

Products: linux_kernel

🛡️What Defenders Should Check

  • Check if you are affected — Review your asset inventory for products listed in CVE-2026-64257.
  • Apply available patches — Visit vendor advisories for the latest security updates.
  • Monitor for exploitation — Check your SIEM/IDS logs for related indicators.

    • Use Vulnios to continuously monitor your exposure to CVE-2026-64257 and similar vulnerabilities.

    References & Sources

  • https://git.kernel.org/stable/c/36bfa52459e45c0d5b668de2f1c91f6dc5c67775
  • https://git.kernel.org/stable/c/445ece263131780dee273d727a4d6f11934feec7
  • https://git.kernel.org/stable/c/4a9d2657d3e05f6ed09c148cb127b4e58702275f
  • https://git.kernel.org/stable/c/57cba95f0e97c6f6e45e6731da30aff091bd7460
  • https://git.kernel.org/stable/c/8986c932905ea508d66da421eb2eb6e676ace1fe
  • https://git.kernel.org/stable/c/fdafa1e68dc75045b7b617e6e7d2854950804d83

    • How Vulnios Detects This

    Vulnios scans for this vulnerability using Trivy and Grype for CVE matching against your container images and OS package manifests. Run a scan against your environment to see whether you are exposed; findings are linked back to the original CVE record so triage starts with the patch path already known.

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    Affected Products

    linux_kernel

    Sources

    Related Threat Alerts

    Frequently Asked Questions

    What is CVE-2026-64257?

    CVE-2026-64257 is a critical-severity vulnerability tracked under the Common Vulnerabilities and Exposures program. In the Linux kernel, the following vulnerability has been resolved:

    smb: client: reject overlapping data areas in SMB2 responses

    Commit 53b7c271f06b ("smb: client: restrict implied bcc[0] exemption

    Am I affected?

    Check whether your environment runs linux_kernel. If you operate any of those, treat yourself as in scope until you have evidence otherwise. A Vulnios scan will identify the exact assets carrying the affected version.

    How urgent is the response?

    Critical: do not wait for your normal patch cycle. Verify exposure today, apply the vendor patch immediately, and add detection rules for any post-exploit indicators.

    How do I remediate?

    Apply the vendor patch listed in the upstream advisory linked under Sources. If the patch is not yet available, follow the vendor-supplied workaround (often a config flag or feature disable) and add detections for the published exploit pattern in your SIEM. Re-scan after the patch lands to confirm the finding clears.

    Where can I track exploitation activity?

    Watch CISA's Known Exploited Vulnerabilities catalog for CVE-2026-64257. Cross-reference with public exploit databases and your own SIEM/IDS for indicator-of-compromise patterns. Vulnios tracks KEV status automatically and surfaces it on the asset findings view.

    How does Vulnios help with this?

    Vulnios continuously cross-references your asset inventory against the live CVE feed (NVD, vendor advisories, CISA KEV, and curated OSINT). When a new CVE matches your environment, you get a prioritized finding with the severity, KEV status, exploit-prediction (EPSS), and a direct path to the vendor patch. You can start a free scan from the homepage.

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