CVE-2018-19518: University of Washington IMAP Toolkit 2007f on UNIX, as used in imap_open() in PHP and other products, launche

This week

HIGH 7.5WATCHLISTUPGRADEMITIGATEDOWNGRADE

CVE-2018-19518 is a high-severity flaw (CVSS 7.5) affecting php, debian linux, uw-imap. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

University of Washington IMAP Toolkit 2007f on UNIX, as used in imap_open() in PHP and other products, launches an rsh command (by means of the imap_rimap function in c-client/imap4r1.c and the tcp_aopen function in osdep/unix/tcp_unix.c) without preventing argument injection, which might allow remote attackers to execute arbitrary OS commands if the IMAP server name is untrusted input (e.g., entered by a user of a web application) and if rsh has

Why this priority

High severity
EPSS top 1%: very likely to be exploited
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	96.1% (top 1%)
CISA exploited list	No
Weakness	CWE-88
Published	2018-11-25
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: canonical · debian · php · uw-imap project

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

Am I affected?

Timeline

2018-11-25 10:29 UTCPublished CVE record published
2026-06-17 01:49 UTCUpdated Record last modified

php php UPGRADE

Affected: >= 5.6.0 and <= 5.6.38 · >= 7.0.0 and <= 7.0.32 · >= 7.1.0 and <= 7.1.24 · >= 7.2.0 and <= 7.2.12

Fixed in: newer than 7.2.12

Safe to downgrade to: a release before 5.6.0

1. Check installed version

apt-cache policy php || rpm -q php || php --version

2. UPGRADE to newer than 7.2.12 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade php

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade php

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.6.0 (Debian / Ubuntu)

apt-cache madison php sudo apt install php=<VERSION_BEFORE_5.6.0> sudo apt-mark hold php

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list php sudo dnf downgrade php-<VERSION_BEFORE_5.6.0> sudo dnf versionlock add php

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

debian debian linux MITIGATE

Affected: 8.0 · 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

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.

uw-imap project uw-imap DOWNGRADE

Affected: 2007f

Fixed in: no fixed release known

Safe to downgrade to: a release before 2007f

1. Check installed version

apt-cache policy uw-imap || rpm -q uw-imap || uw-imap --version

2. No fixed release: DOWNGRADE to a release before 2007f (Debian / Ubuntu)

apt-cache madison uw-imap sudo apt install uw-imap=<VERSION_BEFORE_2007f> sudo apt-mark hold uw-imap

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list uw-imap sudo dnf downgrade uw-imap-<VERSION_BEFORE_2007f> sudo dnf versionlock add uw-imap

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

canonical ubuntu linux MITIGATE

Affected: 16.04 · 18.04 · 19.04

Fixed in: no fixed release known

Safe to downgrade to: a release before 16.04

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.

Exploit-DB: PHP imap_open - Remote Code Execution (Metasploit)
Metasploit: php imap_open Remote Code Execution

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-2018-19518?

php: upgrade to newer than 7.2.12; debian linux: mitigate or apply the listed mitigation; uw-imap: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-19518 being exploited?

CVE-2018-19518 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-2018-19518 affect?

CVE-2018-19518 affects php, debian linux, uw-imap. Severity is high (CVSS 7.5). University of Washington IMAP Toolkit 2007f on UNIX, as used in imap_open() in PHP and other products, launches an rsh command (by means of the imap_rimap function in c-client/imap4r1.c and the tcp_aopen function in osdep/unix/tcp_unix.c) w

How urgent is CVE-2018-19518?

Priority 61/100. High severity; EPSS top 1%: very likely to be exploited; Public exploit reference; On your watchlist

Software pages

PHP vulnerabilities · Ubuntu vulnerabilities · Debian vulnerabilities

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References

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