CVE-2018-1000831: K9Mail version <= v5.600 contains a XML External Entity (XXE) vulnerability in WebDAV response parser that can

Q: How do I fix CVE-2018-1000831?

k-9 mail: upgrade to newer than 5.600. Exact commands for each OS are on this page.

Q: Is CVE-2018-1000831 being exploited?

CVE-2018-1000831 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2018-1000831 affect?

CVE-2018-1000831 affects k-9 mail. Severity is critical (CVSS 10.0). K9Mail version <= v5.600 contains a XML External Entity (XXE) vulnerability in WebDAV response parser that can result in Disclosure of confidential data, denial of service, SSRF, port scanning. This attack appear to be exploitable via malic

Q: How urgent is CVE-2018-1000831?

Priority 60/100. Critical severity; Remotely exploitable, no login, no user action

This week

CRITICAL 10.0REMOTEUPGRADE

CVE-2018-1000831 is a critical-severity flaw (CVSS 10.0) affecting k-9 mail. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

K9Mail version <= v5.600 contains a XML External Entity (XXE) vulnerability in WebDAV response parser that can result in Disclosure of confidential data, denial of service, SSRF, port scanning. This attack appear to be exploitable via malicious WebDAV server or intercept the reponse of a valid WebDAV server.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.9% (top 20%)
CISA exploited list	No
Weakness	CWE-611
Published	2018-12-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: k9mail

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

Am I affected?

Timeline

2018-12-20 15:29 UTCPublished CVE record published
2026-06-17 01:33 UTCUpdated Record last modified

k9mail k-9 mail UPGRADE

Affected: <= 5.600

Fixed in: newer than 5.600

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy k-9-mail || rpm -q k-9-mail || k-9-mail --version

2. UPGRADE to newer than 5.600 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade k-9-mail

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade k-9-mail

Note

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

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-2018-1000831?

k-9 mail: upgrade to newer than 5.600. Exact commands for each OS are on this page.

Is CVE-2018-1000831 being exploited?

CVE-2018-1000831 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-2018-1000831 affect?

CVE-2018-1000831 affects k-9 mail. Severity is critical (CVSS 10.0). K9Mail version <= v5.600 contains a XML External Entity (XXE) vulnerability in WebDAV response parser that can result in Disclosure of confidential data, denial of service, SSRF, port scanning. This attack appear to be exploitable via malic

How urgent is CVE-2018-1000831?

Priority 60/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2019-10741 MEDIUM 4.3 DOWNGRADE K-9 Mail v5.600 can include the original quoted HTML code of a specially crafted, benign looking, email within

References

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