CVE-2020-13163: em-imap 0.5 uses the library eventmachine in an insecure way that allows an attacker to perform a man-in-the-m

This week

HIGH 7.4REMOTEDOWNGRADE

CVE-2020-13163 is a high-severity flaw (CVSS 7.4) affecting em-imap. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

em-imap 0.5 uses the library eventmachine in an insecure way that allows an attacker to perform a man-in-the-middle attack against users of the library. The hostname in a TLS server certificate is not verified.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	7.4 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 44%)
CISA exploited list	No
Weakness	CWE-295
Published	2020-05-19
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: em-imap project

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

Am I affected?

Timeline

2020-05-19 22:15 UTCPublished CVE record published
2026-06-17 02:52 UTCUpdated Record last modified

em-imap project em-imap DOWNGRADE

Affected: 0.5

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.5

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.5 (Debian / Ubuntu)

apt-cache madison em-imap sudo apt install em-imap=<VERSION_BEFORE_0.5> sudo apt-mark hold em-imap

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

dnf --showduplicates list em-imap sudo dnf downgrade em-imap-<VERSION_BEFORE_0.5> sudo dnf versionlock add em-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.

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-2020-13163?

em-imap: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-13163 being exploited?

CVE-2020-13163 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-2020-13163 affect?

CVE-2020-13163 affects em-imap. Severity is high (CVSS 7.4). em-imap 0.5 uses the library eventmachine in an insecure way that allows an attacker to perform a man-in-the-middle attack against users of the library. The hostname in a TLS server certificate is not verified.

How urgent is CVE-2020-13163?

Priority 50/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

References

← Back to latest CVEs