Impact: Moderate Public Date: 2019-06-11 CWE: CWE-592 Bugzilla: 1719344: CVE-2019-12749 dbus: DBusServer DBUS_COOKIE_SHA1 authentication bypass 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.
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2019-12749 from the MITRE CVE dictionary dictionary and NIST NVD.
This flaw is mitigated by the fact that by default, the well-known system dbus-daemon (since 2003) and the well-known session dbus-daemon (in stable releases since dbus 1.10.0 in 2015) only accept the EXTERNAL authentication mechanism, and as a result will reject DBUS_COOKIE_SHA1 at an early stage, before manipulating cookies.
Red Hat Enterprise Linux 7 and 8, both ship dbus >= 1.10 and therefore are affected by this flaw only when system or session dbus-daemons are used under non-standard configurations or by third party users of DBusServer. Either of these use-cases are not applicable to Red Hat Enterprise Linux.
NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.
| CVSS3 Base Score | 6.7 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N |
| Attack Vector | Local |
| Attack Complexity | High |
| Privileges Required | None |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity Impact | High |
| Availability Impact | None |
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise Linux 8 | dbus | Not affected |
| Red Hat Enterprise Linux 7 | dbus | Not affected |
| Red Hat Enterprise Linux 6 | dbus | Out of support scope |
| Red Hat Enterprise Linux 5 | dbus | Out of support scope |
Vulmon