{"id":"CVE-2021-47646","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nRevert \"Revert \"block, bfq: honor already-setup queue merges\"\"\n\nA crash [1] happened to be triggered in conjunction with commit\n2d52c58b9c9b (\"block, bfq: honor already…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nRevert \"Revert \"block, bfq: honor already-setup queue merges\"\"\n\nA crash [1] happened to be triggered in conjunction with commit\n2d52c58b9c9b (\"block, bfq: honor already…","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 < 4.19.238","linux_kernel >= 4.20, < 5.4.189","linux_kernel >= 5.5, < 5.10.110","linux_kernel >= 5.11, < 5.15.33","linux_kernel >= 5.16, < 5.16.19","linux_kernel >= 5.17, < 5.17.2"],"patched":["linux_kernel 5.17.2"],"published":"2025-02-26","updated":"2026-08-11","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2021-47646","references":[{"url":"https://git.kernel.org/stable/c/15729ff8143f8135b03988a100a19e66d7cb7ecd","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4083925bd6dc89216d156474a8076feec904e607","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/65d8a737452e88f251fe5d925371de6d606df613","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/abc2129e646af7b43025d90a071f83043f1ae76c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00282,"epssPercentile":0.20916,"ingestedAt":"2026-08-11T16:47:03.508Z","slug":"CVE-2021-47646","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nRevert \"Revert \"block, bfq: honor already-setup queue merges\"\"\n\nA crash [1] happened to be triggered in conjunction with commit\n2d52c58b9c9b (\"block, bfq: honor already-setup queue merges\"). The\nlatter was then reverted by commit ebc69e897e17 (\"Revert \"block, bfq:\nhonor already-setup queue merges\"\"). Yet, the reverted commit was not\nthe one introducing the bug. In fact, it actually triggered a UAF\nintroduced by a different commit, and now fixed by commit d29bd41428cf\n(\"block, bfq: reset last_bfqq_created on group change\").\n\nSo, there is no point in keeping commit 2d52c58b9c9b (\"block, bfq:\nhonor already-setup queue merges\") out. This commit restores it.\n\n[1] https://bugzilla.kernel.org/show_bug.cgi?id=214503\n\n## Affected\n\n- `linux_kernel < 4.19.238`\n- `linux_kernel >= 4.20, < 5.4.189`\n- `linux_kernel >= 5.5, < 5.10.110`\n- `linux_kernel >= 5.11, < 5.15.33`\n- `linux_kernel >= 5.16, < 5.16.19`\n- `linux_kernel >= 5.17, < 5.17.2`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 5.17.2`","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}