CVE-2019-12749
Description
A flaw was found in dbus. The implementation of DBUS_COOKIE_SHA1 is susceptible to a symbolic link attack. A malicious client with write access to its own home directory could manipulate a ~/.dbus-keyrings symlink to cause the DBusServer to read and write in unintended locations resulting in an authentication bypass. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
Statement
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 6 is affected by this flaw, which can be leveraged to achieve privilege escalation via upstart. This issue has been rated as having important impact for Red Hat Enterprise Linux 6.
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. Red Hat Enterprise Linux 7 and 8 does not ship any affected DBusServer cosumer. However third party applications may be affected.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7 | 7.1 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | None | N/A |
Vector
Red Hat: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability,Access Control
Technical Impact: Read Application Data; Gain Privileges or Assume Identity; Execute Unauthorized Code or Commands
This weakness can lead to the exposure of resources or functionality to unintended actors, possibly providing attackers with sensitive information or even execute arbitrary code.
Acknowledgements
Red Hat would like to thank the D-Bus project for reporting this issue. Upstream acknowledges Joe Vennix (Apple Information Security) as the original reporter.
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