Bamboo Security Advisory 2016-07-20

Bamboo - Deserialisation resulting in remote code execution caused by insufficient restriction on permitted deserialised classes.

Note: As of  September 2014 we are no longer issuing binary bug patches, instead we create new maintenance releases for the major versions we are backporting.

Date of Advisory:  20 Jul 2016 10 AM PDT  (Pacific Time, -7 hours)

CVE ID: 

• CVE-2016-5229 - Deserialisation in Bamboo.

Product: Bamboo

Affected Bamboo product versions:

• 2.3.1 <= version < 5.11.4.1
• 5.12.0 <= version < 5.12.3.1
  
  Note: Bamboo version 5.10.0 and higher are not vulnerable if the "whitelist" option for XStream Serialisation is active. Prior to the fix versions listed below Bamboo defaulted to using a blacklist approach for XStream Serialisation. See Serialization protection methods for information on serialisation settings.

Fixed Bamboo product versions:

• for 5.11.x, Bamboo 5.11.4.1 has been released with a fix for this issue.
• for 5.12.x, Bamboo 5.12.3.1 has been released with a fix for this issue.

Summary of Vulnerability

This advisory discloses a critical severity security vulnerability which was introduced in version 2.3.1 of Bamboo. Versions of Bamboo starting with 2.3.1 before 5.11.4.1 (the fixed version for 5.11.x) and from 5.12.0 before 5.12.3.1 (the fixed version for 5.12.x) are affected by this vulnerability.

Acknowledgements

We would like to credit Moritz Bechler of AgNO3 for reporting this issue to us.

Deserialisation resulting in remote code execution caused by insufficient restriction on permitted deserialised classes (CVE-2016-5229)

Severity

Atlassian rates the severity level of this vulnerability as critical, according to the scale published in our Atlassian severity levels. The scale allows us to rank the severity as critical, high, moderate or low.

This is an independent assessment and you should evaluate its applicability to your own IT environment.

Description

Bamboo had a resource that deserialised input from build agents and did not sufficiently restrict which classes could be deserialised. To exploit this issue, attackers need to have a valid Bamboo agent fingerprint or be able to run code on a Bamboo agent.

All versions of Bamboo from 2.3.1 before 5.11.4.1 (the fixed version for 5.11.x) and from 5.12.0 before 5.12.3.1 (the fixed version for 5.12.x) are affected by this vulnerability. This issue can be tracked here:  BAM-17736 - Getting issue details... STATUS

Mitigation

This issue can be mitigated in Bamboo version 5.10.0 and higher by setting the XStream Serialisation setting to "whitelist" which prior to the fix versions detailed in this advisory was not the default. See Serialization protection methods for information on serialisation settings. 

Fix

We have taken the follow steps to address this issue:

1. Released Bamboo version 5.12.3.1 that contains fixes for this issue.
2. Released Bamboo version 5.11.4.1 that contains fixes for this issue.

What You Need to Do

Upgrade (recommended)

The vulnerabilities and fix versions are described in the description section above. Atlassian recommends that you upgrade to the latest version. This upgrade will automatically reconfigure your Bamboo to use a secure deserialisation mode.

For a full description of the latest version of Bamboo, see the release notes. You can download the latest version of Bamboo from the download centre.

Support

If you have questions or concerns regarding this advisory, please raise a support request at https://support.atlassian.com/.

References