@@ -206,3 +206,11 @@ host model, no upstream kernel fix, mitigated by firewall configuration"
# https://security-tracker.debian.org/tracker/CVE-2021-3714
CVE_STATUS[CVE-2021-3714] = "unpatched: timing side channel inherent to \
KSM page deduplication, only reachable when KSM is enabled and opted into"
+
+# Two mitigation attempts, neither merged; the fs/exec.c logic is
+# unchanged. An absolute, piped or socket kernel.core_pattern (for
+# example systemd-coredump) prevents exploitation.
+# https://www.openwall.com/lists/oss-security/2021/10/20/2
+# https://ubuntu.com/security/CVE-2021-3864
+CVE_STATUS[CVE-2021-3864] = "unpatched: no accepted mainline fix, \
+exploitation requires a relative kernel.core_pattern"
begin_new_exec() resets dumpability to owner-dumpable whenever the real and effective ids match at exec time. A binary exec'd by a setuid program that has already called setuid(0) therefore becomes dumpable as root, and with a relative core_pattern plus an attacker-controlled working directory the resulting core file can be dropped into a privileged directory such as /etc/logrotate.d. Full report with proof of concept: https://www.openwall.com/lists/oss-security/2021/10/20/2 Two fixes were proposed and neither was merged. Waiman Long's patch was judged an ineffective mitigation by Eric W. Biederman and the discussion went quiet in early 2022; Wander Lairson Costa's RFC v2 received design feedback and no v3 followed: https://lore.kernel.org/all/20211221021744.864115-1-longman@redhat.com/ https://lore.kernel.org/all/20211228170910.623156-1-wander@redhat.com/ The flagged logic is unchanged: fs/exec.c still selects TASK_DUMPABLE_OWNER in that case, and fs/coredump.c only applies the suid-safe restriction when dumpable is TASK_DUMPABLE_ROOT, so the dumpable==1 case this CVE describes is not covered. Images that set an absolute path, a pipe or a socket core_pattern are not exploitable. CC: Paul Barker <paul@pbarker.dev> AI-Generated: Uses Claude (claude-opus-5) Signed-off-by: Junjie Cao <junjie.cao@linux.dev> --- v3: - use "unpatched" instead of "upstream-wontfix"; a NAK of one mitigation is not an upstream wontfix of the issue - drop the "NAKed" wording: the discussion went quiet, it was not formally rejected v2: https://lore.kernel.org/openembedded-core/20260803084827.1348810-1-junjie.cao@linux.dev/ meta/recipes-kernel/linux/cve-exclusion.inc | 8 ++++++++ 1 file changed, 8 insertions(+)