CVE Vulnerabilities

CVE-2017-16857

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Published: Dec 05, 2017 | Modified: Apr 20, 2025
CVSS 3.x
8.5
HIGH
Source:
NVD
CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
CVSS 2.x
6 MEDIUM
AV:N/AC:M/Au:S/C:P/I:P/A:P
RedHat/V2
RedHat/V3
Ubuntu

It is possible to bypass the bitbucket auto-unapprove plugin via minimal brute-force because it is relying on asynchronous events on the back-end. This allows an attacker to merge any code into unsuspecting repositories. This affects all versions of the auto-unapprove plugin, however since the auto-unapprove plugin is not bundled with Bitbucket Server it does not affect any particular version of Bitbucket.

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Name Vendor Start Version End Version
Bitbucket_auto_unapprove_plugin Atlassian 1.0.0 (including) 1.0.0 (including)
Bitbucket_auto_unapprove_plugin Atlassian 1.0.0-beta1 (including) 1.0.0-beta1 (including)
Bitbucket_auto_unapprove_plugin Atlassian 1.1.0 (including) 1.1.0 (including)
Bitbucket_auto_unapprove_plugin Atlassian 1.2.0 (including) 1.2.0 (including)
Bitbucket_auto_unapprove_plugin Atlassian 2.0.1 (including) 2.0.1 (including)
Bitbucket_auto_unapprove_plugin Atlassian 2.0.2 (including) 2.0.2 (including)
Bitbucket_auto_unapprove_plugin Atlassian 2.0.4 (including) 2.0.4 (including)
Bitbucket_auto_unapprove_plugin Atlassian 2.1.1 (including) 2.1.1 (including)
Bitbucket_auto_unapprove_plugin Atlassian 2.1.3 (including) 2.1.3 (including)
Bitbucket_auto_unapprove_plugin Atlassian 2.2.0 (including) 2.2.0 (including)
Bitbucket_auto_unapprove_plugin Atlassian 3.0.0 (including) 3.0.0 (including)

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

  • Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
  • Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

References