CVE-2018-15686 | systemd: reexec state injection: fgets() on overlong lines leads to line splitting

Exp

A vulnerability in unit_deserialize of systemd allows an attacker to supply arbitrary state across systemd re-execution via NotifyAccess. This can be used to improperly influence systemd execution and possibly lead to root privilege escalation. Affected releases are systemd versions up to and including 239.

Published: 2018-10-26 Last update: 2025-06-09 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-15686 is rated High Exploit Risk (74.6/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.53%). 2 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

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

Public exploit references (Exploit-DB) for CVE-2018-15686

EDB-ID Source Kind Published Link
45714 exploit_db edb 2018-10-29 Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2018-15686

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 2026-04-01 1.57% 1.53% -0.04%
2 2026-03-21 1.53% 1.57% +0.04%
3 2026-02-26 — 1.53% —

Full EPSS history (27 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-15686

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
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.
 1.8 5.9 [email protected]
7.0 3.0 HIGH
CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
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.
 1.0 5.9 [email protected]
7.2 2.0 HIGH
AV:L/AC:L/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
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.
 3.9 10.0 [email protected]

Weakness enumeration for CVE-2018-15686

OS Trackers for CVE-2018-15686

vendor priority summary link
debian not yet assigned CVE-2018-15686 not yet assigned priority: Debian including 1 source packages (systemd), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2018-15686
gentoo high CVE-2018-15686: 1 GLSA(s) (201810-10), 1 atom(s) (sys-apps/systemd); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2018-15686
redhat medium — https://access.redhat.com/security/cve/CVE-2018-15686
suse medium CVE-2018-15686 severity moderate: SUSE including 688 source package names (0.1.0:libsystemd0-234-24.15.1, 0.1.0:libudev1-234-24.15.1, …), 1417 product×package rows across 216 product lines (Container caasp/v4/389-ds, Container caasp/v4/busybox, … (216 product lines)): Fixed 1260, Known Affected 157. https://www.suse.com/security/cve/CVE-2018-15686/
ubuntu medium CVE-2018-15686 medium priority: Ubuntu including 1 source packages (systemd), 5 status rows across 5 suites (bionic, cosmic, trusty, upstream, xenial): released 3, not-affected 1, pending 1. https://ubuntu.com/security/CVE-2018-15686

Affected software / configurations for CVE-2018-15686

Vendor Product Version Raw CPE
canonical ubuntu_linux 16.04 cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:esm:*:*:*
canonical ubuntu_linux 18.04 cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 18.10 cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*
debian debian_linux 8.0 cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
systemd_project systemd <= 239 cpe:2.3:a:systemd_project:systemd:*:*:*:*:*:*:*:*
oracle communications_cloud_native_core_network_function_cloud_native_environment 1.4.0 cpe:2.3:a:oracle:communications_cloud_native_core_network_function_cloud_native_environment:1.4.0:*:*:*:*:*:*:*

References for CVE-2018-15686

URL Tags
http://www.securityfocus.com/bid/105747 Third Party Advisory VDB Entry
https://access.redhat.com/errata/RHSA-2019:2091 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:3222 Third Party Advisory
https://access.redhat.com/errata/RHSA-2020:0593 Third Party Advisory
https://github.com/systemd/systemd/pull/10519 Patch Third Party Advisory
https://lists.apache.org/thread.html/r1b103833cb5bc8466e24ff0ecc5e75b45a705334ab6a444e64e840a0%40%3Cissues.bookkeeper.apache.org%3E
https://lists.debian.org/debian-lts-announce/2018/11/msg00017.html Mailing List Third Party Advisory
https://security.gentoo.org/glsa/201810-10 Third Party Advisory
https://usn.ubuntu.com/3816-1/ Third Party Advisory
https://www.exploit-db.com/exploits/45714/ Exploit Third Party Advisory VDB Entry
https://www.oracle.com//security-alerts/cpujul2021.html Third Party Advisory
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