{"answers":{"affected":"It affects 1 product.","exploited":"Yes. Attackers have exploited CVE-2021-3493 in the wild since at least 20 Oct 2022.","fix":"Apply the vendor's patch. US federal agencies must fix it by 10 Nov 2022.","what":"CVE-2021-3493 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 17 Apr 2021. It can only be exploited from the same machine or local network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2021-3493 and fix it if it is affected.\n\nWhat it is: CVE-2021-3493 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 17 Apr 2021. It can only be exploited from the same machine or local network, with no action from the victim.\nExploitation: Yes. Attackers have exploited CVE-2021-3493 in the wild since at least 20 Oct 2022.\n\nAffected product: Canonical Ubuntu Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2021-3493/ (Markdown: https://insights.sbomify.com/CVE-2021-3493/index.md)","id":"CVE-2021-3493","markdown":"https://insights.sbomify.com/CVE-2021-3493/index.md","name":"CVE-2021-3493","record":{"aliases":["DEBIAN-CVE-2021-3493","GHSA-2fj2-4h38-3c72","UBUNTU-CVE-2021-3493"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["privilege_escalation"],"network_reachable":"adjacent_or_local","non_default_config":true,"product_category":"Linux kernel","requires_auth":"low_privilege","summary":"Attackers can gain elevated privileges via overlayfs capability validation flaws in the Linux kernel when unprivileged user namespaces and overlay mounts are enabled.","user_interaction":"not_required","vuln_class":"privilege_escalation"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"canonical","cpe":[{"product":"ubuntu_linux","vendor":"canonical"}],"cvss":{"score":8.8,"severity":"high","source":"cna","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","version":"3.1"},"cwes":[{"id":"CWE-863","name":"Incorrect Authorization"},{"id":"CWE-270","name":"Privilege Context Switching Error"}],"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.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":"2021-04-12","github_poc":20,"max_poc_stars":444,"metasploit":1,"nuclei":0,"refs":[{"date":"2021-04-19T20:07:01Z","kind":"github_poc","ref":"https://github.com/briskets/CVE-2021-3493","stars":444,"title":"Ubuntu OverlayFS Local Privesc"},{"date":"2021-07-07T06:16:48Z","kind":"github_poc","ref":"https://github.com/inspiringz/CVE-2021-3493","stars":42,"title":"CVE-2021-3493 Ubuntu OverlayFS Local Privesc (Interactive Bash Shell \u0026 Execute Command Entered)"},{"date":"2021-04-22T02:06:21Z","kind":"github_poc","ref":"https://github.com/oneoy/CVE-2021-3493","stars":3,"title":null},{"date":"2021-10-02T14:44:43Z","kind":"github_poc","ref":"https://github.com/puckiestyle/CVE-2021-3493","stars":2,"title":null},{"date":"2026-07-05T21:11:57Z","kind":"github_poc","ref":"https://github.com/Ayham-Megdadi/Zero-Day-Legacy","stars":2,"title":"A vulnerable Boot-to-Root CTF lab machine simulating a hospital environment. Features a realistic 17-step attack chain including SQL Injection, XSS, Session Hijacking, SSH access, password cracking, privilege escalation via CVE-2021-3493, and full root compromise. Developed as a graduation project at Ajloun National University (ANU), awarded 97%."},{"date":"2021-09-12T12:25:02Z","kind":"github_poc","ref":"https://github.com/cerodah/overlayFS-CVE-2021-3493","stars":1,"title":"2021 kernel vulnerability in Ubuntu."},{"date":"2022-11-29T12:56:00Z","kind":"github_poc","ref":"https://github.com/fei9747/CVE-2021-3493","stars":1,"title":null},{"date":"2021-04-12","kind":"metasploit","ref":"exploit/linux/local/cve_2021_3493_overlayfs","stars":null,"title":"2021 Ubuntu Overlayfs LPE"}],"tier":"exploited"},"has_fix":true,"headline":"Linux Kernel Privilege Escalation","id":"CVE-2021-3493","indexable":true,"kev":{"dateAdded":"2022-10-20","dueDate":"2022-11-10","knownRansomwareCampaignUse":"Unknown","product":"Kernel","requiredAction":"Apply updates per vendor instructions.","vendorProject":"Linux","vulnerabilityName":"Linux Kernel Privilege Escalation Vulnerability"},"kind":"cve","links":{"ecosystem":null,"product":"canonical:ubuntu_linux","products":["canonical:ubuntu_linux"],"type":"privilege_escalation","year":"2021"},"n_packages":0,"n_references":6,"next":{"headline":"Security feature bypass in foreman","id":"CVE-2021-3494"},"packages":[],"prev":{"headline":"Ubuntu linux kernel shiftfs file system double free vulnerability","id":"CVE-2021-3492"},"products":["linux kernel"],"published":"2021-04-17","related":[{"cvss_score":9.8,"headline":"SaltStack Salt Authentication Bypass","id":"CVE-2020-11651","kev_date_added":"2021-11-03","published":"2020-04-30"},{"cvss_score":9.8,"headline":"OpenSMTPD Remote Code Execution","id":"CVE-2020-7247","kev_date_added":"2022-03-25","published":"2020-01-29"},{"cvss_score":9.8,"headline":"Exim Out-of-bounds Write","id":"CVE-2019-16928","kev_date_added":"2022-03-03","published":"2019-09-27"},{"cvss_score":9.8,"headline":"Exim Buffer Overflow","id":"CVE-2018-6789","kev_date_added":"2021-11-03","published":"2018-02-08"},{"cvss_score":9.8,"headline":"Oracle Java SE and Java SE Embedded Remote Code Execution","id":"CVE-2015-2590","kev_date_added":"2022-03-03","published":"2015-07-16"},{"cvss_score":9.8,"headline":"Oracle JRE Remote Code Execution","id":"CVE-2013-0422","kev_date_added":"2022-05-25","published":"2013-01-10"},{"cvss_score":9.8,"headline":"Oracle Java SE Runtime Environment (JRE) Arbitrary Code Execution","id":"CVE-2011-3544","kev_date_added":"2022-03-03","published":"2011-10-19"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"open","licence":"CC0 1.0","name":"CISA KEV"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"},{"class":"attribution","licence":"BSD-3-Clause","name":"Metasploit"},{"class":"open","licence":"CC0","name":"PoC-in-GitHub"}],"ssvc":{"automatable":"no","exploitation":"active","technical_impact":"total"},"state":"PUBLISHED","updated":"2025-10-21","vendors":["Ubuntu"]},"summary":"Attackers can gain elevated privileges via overlayfs capability validation flaws in the Linux kernel when unprivileged user namespaces and overlay mounts are enabled.","url":"https://insights.sbomify.com/CVE-2021-3493/"}