What is CVE-2018-1000831?

CVE-2018-1000831 is a critical-severity vulnerability in K9mail K-9 Mail, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 10.0/10. Published 2018-12-20.

How severe is CVE-2018-1000831?

Critical severity. CVSS v3 base score is 10.0 out of 10.

XXE in K9mail K-9 Mail

CVE-2018-1000831

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.

Vulnerability class: XXE (XML External Entity)

Published 2018-12-20 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 10.0 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.019 (79.0th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 79th percentile — 79.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.019 · newest: 0.019 · change: 0.000

Affected products

K9mail K-9 Mail

Weakness classification (CWE)

CWE-611 — Improper Restriction of XML External Entity Reference (XXE)

References

github.com/k9mail/k-9/issues/3681 (Third Party Advisory, Issue Tracking)
0dd.zone/2018/10/28/k9mail-XXE-MitM/ (Third Party Advisory)

Frequently asked questions

What is CVE-2018-1000831?: CVE-2018-1000831 is a critical-severity vulnerability in K9mail K-9 Mail, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 10.0/10. Published 2018-12-20.
How severe is CVE-2018-1000831?: Critical severity. CVSS v3 base score is 10.0 out of 10.