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FedoraOperating system · Fedoraproject

CVE-2019-11356

CRITICAL · 9.8 CVSS v3.1 Published 2019-06-03
Fix available
A fix is available. Upgrade to after 3.0.9 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
The CalDAV feature in httpd in Cyrus IMAP 2.5.x through 2.5.12 and 3.0.x through 3.0.9 allows remote attackers to execute arbitrary code via a crafted HTTP PUT operation for an event with a long iCalendar property name.

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

The CalDAV HTTP handler in Cyrus IMAP's httpd component contains a memory corruption vulnerability when processing iCalendar property names during HTTP PUT operations. A remote attacker can send a crafted PUT request with an excessively long iCalendar property name to trigger a buffer overflow and achieve arbitrary code execution with the privileges of the httpd process.

MitigationUpgrade Cyrus IMAP to version 2.5.13 or later for the 2.5.x branch, or 3.0.10 or later for the 3.0.x branch. If immediate patching is not possible, consider restricting network access to the CalDAV endpoints via firewall rules or network segmentation.

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
FedoraOperating system
Affected:= 29= 30
Debian LinuxOperating system
Affected:= 9.0
Ubuntu LinuxOperating system
Affected:= 18.04
Enterprise LinuxOperating system
Affected:= 8.0
Enterprise Linux EusOperating system
Affected:= 8.1= 8.2= 8.4
Enterprise Linux Server AusOperating system
Affected:= 8.2= 8.4
Enterprise Linux Server TusOperating system
Affected:= 8.2= 8.4
ImapApplication
Affected:>= 2.5.0, <= 2.5.12>= 3.0.0, <= 3.0.9

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
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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 Cyrus IMAP version
    Run 'cyrus-imapd -v' or check the package version with 'rpm -q cyrus-imapd' on RHEL/Fedora, or 'dpkg -l cyrus-imapd' on Debian/Ubuntu
    Affected if The installed version is 2.5.0 through 2.5.12, or 3.0.0 through 3.0.9
  2. Confirm CalDAV service is enabled
    Examine /etc/cyrus.conf and /etc/imapd.conf for CalDAV-related service entries, or run 'cyrus-imapd -C all' to list active services
    Affected if The CalDAV or httpd service is listed as enabled in the configuration
  3. Identify CalDAV HTTP endpoint configuration
    Search for 'CalDAV' or 'http' directives in /etc/imapd.conf and check /etc/httpd.conf for HTTP handlers exposing CalDAV paths (typically /caldav or /iCalendar)
    Affected if CalDAV HTTP endpoints are configured and exposed via the httpd component
  4. Verify network exposure of the HTTP service
    Check which addresses the httpd process binds to using 'netstat -tlnp | grep http' or 'ss -tlnp | grep http' to determine if CalDAV is accessible remotely
    Affected if The CalDAV HTTP endpoint is bound to a non-loopback address and reachable over the network

The environment is affected if Cyrus IMAP version is within the vulnerable ranges AND CalDAV HTTP endpoints are configured and accessible.

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.

dbcve · scoped
Upgrade available Upgrade to a release after 3.0.9
Interim mitigation

Upgrade Cyrus IMAP to version 2.5.13 or later for the 2.5.x branch, or 3.0.10 or later for the 3.0.x branch. If immediate patching is not possible, consider restricting network access to the CalDAV endpoints via firewall rules or network segmentation.

Recommended fix High confidence

Cyrus IMAP 2.5.13 or later, or 3.0.10 or later (depending on which branch you are using)

  1. Identify the currently installed Cyrus IMAP version using your package manager (e.g., `rpm -q cyrus-imapd` or `dpkg -l | grep cyrus`)
  2. For RHEL/CentOS/Enterprise Linux: Run `dnf update cyrus-imapd` or `yum update cyrus-imapd` to apply the latest available security patches
  3. For Fedora: Run `dnf update` to get the latest package versions
  4. For Debian/Ubuntu: Run `apt-get update && apt-get upgrade` or `apt-get install cyrus-imapd` to install the fixed package
  5. After updating, restart the cyrus-imapd service using `systemctl restart cyrus-imapd` or the appropriate service command for your system
  6. Verify the new version is installed and the service is running properly
Caveat Minor version upgrades within the same major.minor branch typically have backward compatibility, but test in a non-production environment first to ensure configuration compatibility

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fedora Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,380
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,808.

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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-2019-11356 in production — separate from our analysis above.

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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