{"id":"CVE-2021-34556","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-34556","generatedAt":"2026-10-27T20:54:18.995Z","title":"In the Linux kernel through 5.13.7, an unprivileged BPF program can obtain sensitive information from kernel memory via a Speculative Store Bypass side-channel attack because the protection mechanism neglects the possibility of uninitialized memory…","description":"In the Linux kernel through 5.13.7, an unprivileged BPF program can obtain sensitive information from kernel memory via a Speculative Store Bypass side-channel attack because the protection mechanism neglects the possibility of uninitialized memory locations on the BPF stack.","published":"2021-08-02T05:15:08.000Z","lastModified":"2026-10-08T21:17:36.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":5.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"},"cwe":["CWE-203"],"affected":["linux/linux kernel","fedoraproject/fedora","debian/debian linux"],"epss":{"score":0.00419,"percentile":0.36007,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.42%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"http://www.openwall.com/lists/oss-security/2021/08/01/3","tags":["Mailing List"],"source":"cve@mitre.org"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=2039f26f3aca5b0e419b98f65dd36481337b86ee","tags":["Patch","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=f5e81d1117501546b7be050c5fbafa6efd2c722c","tags":["Patch","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://lists.debian.org/debian-lts-announce/2021/10/msg00010.html","tags":["Mailing List","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/565ZS55ZFEN62WVRRORT7R63RXW5F4T4/","source":"cve@mitre.org"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6JKK6XNRZX5BT5QVYOKGVJ2BHFZAP5EX/","source":"cve@mitre.org"},{"url":"http://www.openwall.com/lists/oss-security/2021/08/01/3","tags":["Mailing List"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=2039f26f3aca5b0e419b98f65dd36481337b86ee","tags":["Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=f5e81d1117501546b7be050c5fbafa6efd2c722c","tags":["Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2021/10/msg00010.html","tags":["Mailing List","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/565ZS55ZFEN62WVRRORT7R63RXW5F4T4/","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6JKK6XNRZX5BT5QVYOKGVJ2BHFZAP5EX/","source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-34556","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}