dbcve.org
Ubuntu LinuxOperating system · Canonical

CVE-2019-12749

HIGH · 7.1 CVSS v3.1 Published 2019-06-11
Fix available
A fix is available. Upgrade to 1.10.28 / 1.12.16 or later.
See remediation →
73/100
Remediation priority · Elevated
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
dbus before 1.10.28, 1.12.x before 1.12.16, and 1.13.x before 1.13.12, as used in DBusServer in Canonical Upstart in Ubuntu 14.04 (and in some, less common, uses of dbus-daemon), allows cookie spoofing because of symlink mishandling in the reference implementation of DBUS_COOKIE_SHA1 in the libdbus library. (This only affects the DBUS_COOKIE_SHA1 authentication mechanism.) A malicious client with write access to its own home directory could manipulate a ~/.dbus-keyrings symlink to cause a DBusServer with a different uid to read and write in unintended locations. In the worst case, this could result in the DBusServer reusing a cookie that is known to the malicious client, and treating that cookie as evidence that a subsequent client connection came from an attacker-chosen uid, allowing authentication bypass.

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

A symlink handling flaw in the DBUS_COOKIE_SHA1 authentication mechanism of libdbus allows a malicious client with write access to their home directory to manipulate the ~/.dbus-keyrings symlink, causing a DBusServer running as a different uid to read/write cookies in attacker-controlled locations. This enables cookie reuse and authentication bypass by tricking the server into accepting a known cookie as proof of a different user identity.

MitigationUpgrade dbus to version 1.10.28/1.12.16/1.13.12 or later to obtain the patch. If immediate upgrade is not feasible, audit and restrict write access to ~/.dbus-keyrings and ensure it is a real directory, not a symlink.

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
Ubuntu LinuxOperating system
Affected:= 16.04= 18.04= 18.10= 19.04
DbusApplication
Affected:< 1.10.28>= 1.12.0, < 1.12.16>= 1.13.0, < 1.13.12

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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

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 dbus version
    Run 'dbus-daemon --version' or 'pkg-config --modversion libdbus' to get the version number
    Affected if The version falls outside the fixed releases: not 1.10.28+, 1.12.16+, or 1.13.12+
  2. Verify ~/.dbus-keyrings is a symlink
    Run 'ls -la ~/.dbus-keyrings' and check if the entry shows an arrow (->) indicating a symlink, or use 'file ~/.dbus-keyrings'
    Affected if The path resolves to a symlink rather than a real directory (the 'l' permission prefix and '->' notation in ls output indicate a symlink)
  3. Check write permissions on ~/.dbus-keyrings parent directory
    Run 'ls -lad ~' and check group/other write permissions on the home directory
    Affected if The home directory or ~/.dbus-keyrings is writable by users other than the owner, allowing a malicious local user to replace or create the symlink
  4. Determine if DBUS_COOKIE_SHA1 authentication is in use
    Check dbus configuration files in /etc/dbus-1/ or ~/.dbus/ for auth settings, or inspect running dbus-daemon processes with 'ps aux | grep dbus-daemon' and review configuration
    Affected if The system uses DBUS_COOKIE_SHA1 (the default in many setups) rather than DBUS_COOKIE_SHA1_STRING or other mechanisms; note that any use of the cookie mechanism relies on ~/.dbus-keyrings

You are affected if your dbus version is unpatched AND ~/.dbus-keyrings is a symlink AND an untrusted user has write access to your home directory to manipulate that symlink.

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 1.10.28 / 1.12.16 / 1.13.12 or later
Fixed in 1.10.281.12.161.13.12
Interim mitigation

Upgrade dbus to version 1.10.28/1.12.16/1.13.12 or later to obtain the patch. If immediate upgrade is not feasible, audit and restrict write access to ~/.dbus-keyrings and ensure it is a real directory, not a symlink.

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
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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-2019-12749 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