CVE-2018-20836

An issue was discovered in the Linux kernel before 4.20. There is a race condition in smp_task_timedout() and smp_task_done() in drivers/scsi/libsas/sas_expander.c, leading to a use-after-free.

Published: 2019-05-07 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-20836 is rated High Risk (65.4/100): CVSS High severity, with high exploitation likelihood (EPSS 5.11%, 91th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +1.05% over the last day, indicating growing attacker interest. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2018-20836

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 4.06% 5.11% +1.05%
2 2026-05-29 3.83% 4.06% +0.23%
3 2026-05-26 — 3.83% —

Full EPSS history (32 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-20836

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.1 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.2 5.9 [email protected]
9.3 2.0 HIGH
AV:N/AC:M/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 8.6 10.0 [email protected]

Weakness enumeration for CVE-2018-20836

OS Trackers for CVE-2018-20836

vendor priority summary link
debian not yet assigned CVE-2018-20836 not yet assigned priority: Debian including 1 source packages (linux), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2018-20836
redhat medium — https://access.redhat.com/security/cve/CVE-2018-20836
suse low CVE-2018-20836 severity low: SUSE including 345 source package names (bpftool-3.10.0-1160.el7, cluster-md-kmp-default-4.12.14-120.1, …), 722 product×package rows across 112 product lines (Image SLES12-SP5-Azure-BYOS, Image SLES12-SP5-Azure-Basic-On-Demand, … (112 product lines)): Fixed 644, Known Not Affected 78. https://www.suse.com/security/cve/CVE-2018-20836/
ubuntu low CVE-2018-20836 low priority: Ubuntu including 92 source packages (linux, linux-aws, …), 856 status rows across 12 suites (bionic, cosmic, disco, eoan, focal, jammy, noble, oracular, plucky, trusty, upstream, xenial): DNE 570, not-affected 149, released 125, ignored 12. https://ubuntu.com/security/CVE-2018-20836

Affected software / configurations for CVE-2018-20836

Vendor Product Version Raw CPE
linux linux_kernel < 3.16.72 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 3.17, < 3.18.140 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 3.19, < 4.4.180 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 4.5, < 4.9.175 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 4.10, < 4.14.118 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 4.15, < 4.19.42 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
canonical ubuntu_linux 16.04 cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:esm:*:*:*
debian debian_linux 8.0 cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
f5 traffix_signaling_delivery_controller 5.0.0 cpe:2.3:a:f5:traffix_signaling_delivery_controller:5.0.0:*:*:*:*:*:*:*
f5 traffix_signaling_delivery_controller 5.1.0 cpe:2.3:a:f5:traffix_signaling_delivery_controller:5.1.0:*:*:*:*:*:*:*
netapp active_iq_unified_manager >= 9.5 cpe:2.3:a:netapp:active_iq_unified_manager:*:*:*:*:*:vmware_vsphere:*:*
netapp snapprotect — cpe:2.3:a:netapp:snapprotect:-:*:*:*:*:*:*:*
netapp solidfire_\&_hci_management_node — cpe:2.3:a:netapp:solidfire_\&_hci_management_node:-:*:*:*:*:*:*:*
netapp solidfire_\&_hci_storage_node — cpe:2.3:a:netapp:solidfire_\&_hci_storage_node:-:*:*:*:*:*:*:*
netapp storage_replication_adapter_for_clustered_data_ontap — cpe:2.3:a:netapp:storage_replication_adapter_for_clustered_data_ontap:-:*:*:*:*:vmware_vsphere:*:*
netapp vasa_provider_for_clustered_data_ontap >= 7.2 cpe:2.3:a:netapp:vasa_provider_for_clustered_data_ontap:*:*:*:*:*:*:*:*
netapp virtual_storage_console >= 7.2 cpe:2.3:a:netapp:virtual_storage_console:*:*:*:*:*:vmware_vsphere:*:*
netapp hci_compute_node — cpe:2.3:h:netapp:hci_compute_node:-:*:*:*:*:*:*:*
opensuse leap 15.0 cpe:2.3:o:opensuse:leap:15.0:*:*:*:*:*:*:*
opensuse leap 15.1 cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*

References for CVE-2018-20836

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00014.html Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00025.html Mailing List Third Party Advisory
http://www.securityfocus.com/bid/108196 Third Party Advisory VDB Entry
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=b90cd6f2b905905fb42671009dc0e27c310a16ae Patch Vendor Advisory
https://github.com/torvalds/linux/commit/b90cd6f2b905905fb42671009dc0e27c310a16ae Patch Vendor Advisory
https://lists.debian.org/debian-lts-announce/2019/08/msg00016.html Mailing List Third Party Advisory
https://lists.debian.org/debian-lts-announce/2019/08/msg00017.html Mailing List Third Party Advisory
https://seclists.org/bugtraq/2019/Aug/13 Mailing List Third Party Advisory
https://seclists.org/bugtraq/2019/Aug/18 Mailing List Third Party Advisory
https://security.netapp.com/advisory/ntap-20190719-0003/ Third Party Advisory
https://support.f5.com/csp/article/K11225249 Third Party Advisory
https://usn.ubuntu.com/4076-1/ Third Party Advisory
https://www.debian.org/security/2019/dsa-4495 Third Party Advisory
https://www.debian.org/security/2019/dsa-4497 Third Party Advisory
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