{"id":"CVE-2021-33033","title":"The Linux kernel before 5.11.14 has a use-after-free in cipso_v4_genopt in net/ipv4/cipso_ipv4.c because the CIPSO and CALIPSO refcounting for the DOI definitions is mishandled, aka CID-ad5d07f4a9cd","summary":"The Linux kernel before 5.11.14 has a use-after-free in cipso_v4_genopt in net/ipv4/cipso_ipv4.c because the CIPSO and CALIPSO refcounting for the DOI definitions is mishandled, aka CID-ad5d07f4a9cd. This leads to writing an arbitrary va…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-416"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 2.6.28, < 4.9.298","linux_kernel >= 4.10, < 4.14.226","linux_kernel >= 4.15, < 4.19.181","linux_kernel >= 4.20, < 5.4.106","linux_kernel >= 5.5, < 5.10.24","linux_kernel >= 5.11, < 5.11.7"],"patched":["linux_kernel 5.11.7"],"published":"2021-05-14","updated":"2026-08-05","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2021-33033","references":[{"url":"https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.14","label":"cve@mitre.org"},{"url":"https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.7","label":"cve@mitre.org"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1165affd484889d4986cf3b724318935a0b120d8","label":"cve@mitre.org"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad5d07f4a9cd671233ae20983848874731102c08","label":"cve@mitre.org"},{"url":"https://sites.google.com/view/syzscope/kasan-use-after-free-read-in-cipso_v4_genopt","label":"cve@mitre.org"},{"url":"https://syzkaller.appspot.com/bug?id=96e7d345748d8814901c91cd92084ed04b46701e","label":"cve@mitre.org"},{"url":"https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.14","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.7","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1165affd484889d4986cf3b724318935a0b120d8","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad5d07f4a9cd671233ae20983848874731102c08","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://sites.google.com/view/syzscope/kasan-use-after-free-read-in-cipso_v4_genopt","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://syzkaller.appspot.com/bug?id=96e7d345748d8814901c91cd92084ed04b46701e","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd"],"epss":0.00566,"epssPercentile":0.4578,"ingestedAt":"2026-08-05T18:50:24.770Z","slug":"CVE-2021-33033","body":"## Overview\n\nThe Linux kernel before 5.11.14 has a use-after-free in cipso_v4_genopt in net/ipv4/cipso_ipv4.c because the CIPSO and CALIPSO refcounting for the DOI definitions is mishandled, aka CID-ad5d07f4a9cd. This leads to writing an arbitrary value.\n\n## Affected\n\n- `linux_kernel >= 2.6.28, < 4.9.298`\n- `linux_kernel >= 4.10, < 4.14.226`\n- `linux_kernel >= 4.15, < 4.19.181`\n- `linux_kernel >= 4.20, < 5.4.106`\n- `linux_kernel >= 5.5, < 5.10.24`\n- `linux_kernel >= 5.11, < 5.11.7`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 5.11.7`","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}