{
  "threat_severity" : "Moderate",
  "public_date" : "2021-08-01T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: BPF program can obtain sensitive information from kernel memory via a speculative store bypass side-channel attack because of the possibility of uninitialized memory locations on the BPF stack",
    "id" : "1989212",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=1989212"
  },
  "cvss3" : {
    "cvss3_base_score" : "4.4",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N",
    "status" : "draft"
  },
  "cwe" : "CWE-200",
  "details" : [ "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.", "A flaw was found in the Linux kernel, where a BPF program can obtain sensitive information from kernel memory via a Speculative Store Bypass side-channel attack. This issue occurs when the protection mechanism neglects the possibility of uninitialized memory locations on the BPF stack. The highest threat from this vulnerability is to confidentiality." ],
  "statement" : "For the Red Hat Enterprise Linux 8 fixed with the Errata RHSA-2021:4356.",
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 5",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:5"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Will not fix",
    "package_name" : "kernel-alt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2021-34556\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-34556\nhttp://www.openwall.com/lists/oss-security/2021/08/01/3" ],
  "name" : "CVE-2021-34556",
  "mitigation" : {
    "value" : "The default Red Hat Enterprise Linux kernel setting prevents unprivileged users from being able to use eBPF via the kernel.unprivileged_bpf_disabled sysctl. As such, exploiting this issue would require a privileged user with CAP_SYS_ADMIN or root.\nFor the Red Hat Enterprise Linux 7 the eBPF for unprivileged users is always disabled. For the Red Hat Enterprise Linux 8 to confirm the current state, inspect the sysctl with the command:\ncat /proc/sys/kernel/unprivileged_bpf_disabled\nThe setting of 1 (default) would mean that unprivileged users cannot use eBPF. Otherwise, to disable eBPF for unprivileged users, add:\nkernel.unprivileged_bpf_disabled = 1\nTo the file \"/etc/sysctl.d/disable-ebpf.conf\"\nThen running the following command as root:\n# sudo sysctl --system",
    "lang" : "en:us"
  },
  "csaw" : false
}