CVE-2018-18956: The ProcessMimeEntity function in util-decode-mime.c in Suricata 4.x before 4.0.6 allows remote attackers to c

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HIGH 7.5REMOTEUPGRADE

CVE-2018-18956 is a high-severity flaw (CVSS 7.5) affecting suricata. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The ProcessMimeEntity function in util-decode-mime.c in Suricata 4.x before 4.0.6 allows remote attackers to cause a denial of service (segfault and daemon crash) via crafted input to the SMTP parser, as exploited in the wild in November 2018.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.8% (top 13%)
CISA exploited list	No
Weakness	CWE-119
Published	2018-11-05
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: suricata-ids

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

Am I affected?

Timeline

2018-11-05 21:29 UTCPublished CVE record published
2026-06-17 01:48 UTCUpdated Record last modified

suricata-ids suricata UPGRADE

Affected: >= 4.0.0 and < 4.0.6

Fixed in: 4.0.6

Safe to downgrade to: a release before 4.0.0

1. Check installed version

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

2. UPGRADE to 4.0.6 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade suricata

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 4.0.0 (Debian / Ubuntu)

apt-cache madison suricata sudo apt install suricata=<VERSION_BEFORE_4.0.0> sudo apt-mark hold suricata

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

dnf --showduplicates list suricata sudo dnf downgrade suricata-<VERSION_BEFORE_4.0.0> sudo dnf versionlock add suricata

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.

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-2018-18956?

suricata: upgrade to 4.0.6. Exact commands for each OS are on this page.

Is CVE-2018-18956 being exploited?

CVE-2018-18956 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-2018-18956 affect?

CVE-2018-18956 affects suricata. Severity is high (CVSS 7.5). The ProcessMimeEntity function in util-decode-mime.c in Suricata 4.x before 4.0.6 allows remote attackers to cause a denial of service (segfault and daemon crash) via crafted input to the SMTP parser, as exploited in the wild in November 20

How urgent is CVE-2018-18956?

Priority 53/100. High severity; Remotely exploitable, no login, no user action

Software pages

Suricata and Snort vulnerabilities

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References

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