CVE-2018-18556: A privilege escalation issue was discovered in VyOS 1.1.8

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CRITICAL 9.9MITIGATE

CVE-2018-18556 is a critical-severity flaw (CVSS 9.9) affecting vyos. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A privilege escalation issue was discovered in VyOS 1.1.8. The default configuration also allows operator users to execute the pppd binary with elevated (sudo) permissions. Certain input parameters are not properly validated. A malicious operator user can run the binary with elevated permissions and leverage its improper input validation condition to spawn an attacker-controlled shell with root privileges.

Why this priority

Critical severity
EPSS top 3%: very likely to be exploited
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.9 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	15.4% (top 3%)
CISA exploited list	No
Published	2018-12-17
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: vyos

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-12-17 19:29 UTCPublished CVE record published
2026-06-17 01:47 UTCUpdated Record last modified

vyos vyos MITIGATE

Affected: 1.1.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.1.8

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Metasploit: VyOS restricted-shell Escape and Privilege Escalation

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2018-18556?

vyos: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-18556 being exploited?

CVE-2018-18556 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2018-18556 affect?

CVE-2018-18556 affects vyos. Severity is critical (CVSS 9.9). A privilege escalation issue was discovered in VyOS 1.1.8. The default configuration also allows operator users to execute the pppd binary with elevated (sudo) permissions. Certain input parameters are not properly validated. A malicious op

How urgent is CVE-2018-18556?

Priority 64/100. Critical severity; EPSS top 3%: very likely to be exploited; Public exploit reference

Software pages

Sudo vulnerabilities

Related CVEs

CVE-2018-18555 CRITICAL 9.9 MITIGATE A sandbox escape issue was discovered in VyOS 1.1.8

References

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