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K 9 MailApplication · K9mail

CVE-2018-1000831

CRITICAL · 10.0 CVSS v3.0 Published 2018-12-20
Fix available
A fix is available. Upgrade to after 5.600 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

K9Mail versions v5.600 and below contain an XML External Entity (XXE) vulnerability in the WebDAV response parser. The application parses XML responses from WebDAV servers without disabling external entity processing, allowing an attacker to inject malicious XML that can access local files, perform SSRF, port scanning, or cause denial of service.

MitigationUpgrade to K9Mail version v5.601 or later, which should include proper XML parser configuration to disable external entity processing. Until then, avoid connecting to untrusted WebDAV servers.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
K 9 MailApplication
Affected:<= 5.600

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed K9Mail version
    Open K9Mail, go to Settings > About > Version. Note the version number displayed.
    Affected if Version number is 5.600 or lower (e.g., 5.600, 5.503, 5.400, etc.)
  2. Confirm WebDAV account configuration
    Open K9Mail, go to Settings > Accounts. Look for any accounts configured with WebDAV (often labeled as WebDAV, CalDAV, or CardDAV servers).
    Affected if One or more WebDAV/CalDAV/CardDAV accounts are configured and enabled

If K9Mail version is 5.600 or below AND a WebDAV-based account is configured, the environment is affected by this XXE vulnerability in the WebDAV XML parser.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to a release after 5.600
Interim mitigation

Upgrade to K9Mail version v5.601 or later, which should include proper XML parser configuration to disable external entity processing. Until then, avoid connecting to untrusted WebDAV servers.

Fix this in K 9 Mail Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2018-1000831 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data