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    CVE-2021-3493

    The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges.

    Published:Apr 16, 2021
    Last Modified:Oct 28, 2025
    EPS:Apr 17, 2021
    EPSS Score:0.7749
    CVSS Score:8.8

    CISA Notification

    Description

    The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges.

    Required Action:

    Apply updates per vendor instructions.

    Notes:

    No extra notes provided.

    Due Date
    Nov 10, 2022
    1401 days ago
    Alert Date
    Oct 20, 2022
    1422 days ago

    Affected Products

    Vendor
    Canonical
    Product
    Ubuntu Linux

    Exploits

    http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.htmlhttp://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.htmlhttp://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.htmlhttp://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.htmlhttps://github.com/0xlane/CVE-2021-3493https://github.com/Abdennour-py/CVE-2021-3493https://github.com/Ayham-Megdadi/Zero-Day-Legacyhttps://github.com/briskets/CVE-2021-3493https://github.com/cerodah/overlayFS-CVE-2021-3493https://github.com/cyberx-1/OverlayFS-CVE-2021-3493https://github.com/derek-turing/CVE-2021-3493https://github.com/fathallah17/OverlayFS-CVE-2021-3493https://github.com/fei9747/CVE-2021-3493https://github.com/George-Yanni/DeepRoothttps://github.com/iamz24/CVE-2021-3493_CVE-2022-3357https://github.com/inspiringz/CVE-2021-3493https://github.com/iqbalhussainas/OverlayFS-LPE-Exploithttps://github.com/oneoy/CVE-2021-3493https://github.com/pmihsan/OverlayFS-CVE-2021-3493https://github.com/ptkhai15/OverlayFS---CVE-2021-3493https://github.com/puckiestyle/CVE-2021-3493https://github.com/r3dw4n48m3d/CVE-2021-3493-Exploithttps://github.com/smallkill/CVE-2021-3493https://github.com/Sornphut/OverlayFS---CVE-2021-3493https://github.com/spideyctf/UbuntuTouchSecurityVAPTReporthttps://github.com/WhatsWrongAndWhy/CVE-2021-3493

    Related CVEs

    CVE-2026-13476 (CVSS 7.3) — IBM Informix Dynamic Server 14.10, 15.0, and 12.10 could allow an unauthenticated user to execute arbitrary co…
    CVE-2026-13367 (CVSS 7.8) — IBM Informix Dynamic Server 14.10, and 15.0 contain a local privilege escalation vulnerability in the oninit s…
    CVE-2026-47337 (CVSS 3.3) — Ubuntu Linux 6.8, 6.17 and 7.0 contain SAUCE patches with a possible NULL pointer dereference in the handling …
    CVE-2026-47336 (CVSS 3.3) — Ubuntu Linux 6.8 contains SAUCE patches with a possible use of an uninitialized variable in AppArmor AF_INET/A…
    CVE-2026-47335 (CVSS 5.5) — Ubuntu Linux 6.8 contains SAUCE patches with a possible NULL pointer dereference in the handling of AppArmor n…
    CVE-2026-47334 (CVSS 5.5) — Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which incorrectly sleep while holding a spinlock…
    CVE-2026-47333 (CVSS 7.8) — Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which can potentially incorrectly compute the si…
    CVE-2026-47332 (CVSS 5.5) — Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which incorrectly validate the size of an intern…
    CVE-2026-47331 (CVSS 7.8) — Ubuntu Linux 6.8 contains AppArmor SAUCE patches which fail to acquire a lock when modifying a linked list. An…
    CVE-2026-47330 (CVSS 3.3) — Ubuntu Linux 6.8, 7.17 and 7.0 contain AppArmor SAUCE patches which can, under certain circumstances, use an u…

    References

    http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html
    http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html
    http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52
    https://ubuntu.com/security/notices/USN-4917-1
    https://www.openwall.com/lists/oss-security/2021/04/16/1
    http://packetstormsecurity.com/files/162434/Kernel-Live-Patch-Security-Notice-LSN-0076-1.html
    http://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html
    http://packetstormsecurity.com/files/165151/Ubuntu-Overlayfs-Local-Privilege-Escalation.html
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52
    https://ubuntu.com/security/notices/USN-4917-1
    https://www.openwall.com/lists/oss-security/2021/04/16/1
    https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3493

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High