A vulnerability in the Backblaze Client allows a local user to make the system not bootable by creating a link from Backblaze's folder to Windows OS system files during a backup. Successful exploitation requires an administrator-level system change that results in the absence of specific Windows OS security controls. This vulnerability is due to improper link resolution.

Impact

Linux and Mac releases of the SDK version 1.14.0 and below contain a key disclosure vulnerability that, in certain conditions, can be exploited by local attackers through a time-of-check-time-of-use (TOCTOU) race condition.

SDK users of the SqliteAccountInfo format are vulnerable while users of the InMemoryAccountInfo format are safe. The SqliteAccountInfo saves API keys (and bucket name-to-id mapping) in a local database file ($XDGCONFIGHOME/b2/accountinfo, ~/.b2accountinfo or a user-defined path). When first created, the file is world readable and is (typically a few milliseconds) later altered to be private to the user. If the directory containing the file is readable by a local attacker then during the brief period between file creation and permission modification, a local attacker can race to open the file and maintain a handle to it. This allows the local attacker to read the contents after the file after the sensitive information has been saved to it.

Consumers of this SDK who rely on it to save data using SqliteAccountInfo class should upgrade to the latest version of the SDK. Those who believe a local user might have opened a handle using this race condition, should remove the affected database files and regenerate all application keys.

Patches Users should upgrade to b2-sdk-python 1.14.1 or later.

For more information See the related advisory in the B2 Command Line Tool, a consumer of this SDK.

If you have any questions or comments about this advisory: Open an issue in b2-sdk-python Email us at security@backblaze.com

Impact

Linux and Mac releases of the B2 command-line tool version 3.2.0 and below contain a key disclosure vulnerability that, in certain conditions, can be exploited by local attackers through a time-of-check-time-of-use (TOCTOU) race condition.

The command line tool saves API keys (and bucket name-to-id mapping) in a local database file ($XDGCONFIGHOME/b2/accountinfo, ~/.b2accountinfo or a user-defined path) when b2 authorize-account is first run. This happens regardless of whether a valid key is provided or not. When first created, the file is world readable and is (typically a few milliseconds) later altered to be private to the user. If the directory is readable by a local attacker and the user did not yet run b2 authorize-account then during the brief period between file creation and permission modification, a local attacker can race to open the file and maintain a handle to it. This allows the local attacker to read the contents after the file after the sensitive information has been saved to it.

Remediation

Users that have not yet run b2 authorize-account should upgrade to B2 Command-Line Tool v3.2.1 before running it.

Users that have run b2 authorize-account are safe if at the time of the file creation no other local users had read access to the local configuration file.

Users that have run b2 authorize-account where the designated path could be opened by another local user should upgrade to B2 Command-Line Tool v3.2.1 and remove the database and regenerate all application keys. Note that b2 clear-account does not remove the database file and it should not be used to ensure that all open handles to the file are invalidated.

Workarounds If B2 Command-Line Tool cannot be upgraded to v3.2.1 due to a dependency conflict, a binary release can be used instead. Alternatively a new version could be installed within a virtualenv, or the permissions can be changed to prevent local users from opening the database file.

For more information If you have any questions or comments about this advisory: Open an issue in B2 Command-Line Tool mentioning the CVE id in the issue title Email us at security@backblaze.com

Backblaze for Windows and Backblaze for macOS before 7.0.0.439 suffer from improper privilege management in bztransmit helper due to lack of permission handling and validation before creation of client update directories allowing for local escalation of privilege via rogue client update binary.

Backblaze for Windows before 7.0.1.433 and Backblaze for macOS before 7.0.1.434 suffer from improper certificate validation in bztransmit helper due to hardcoded whitelist of strings in URLs where validation is disabled leading to possible remote code execution via client update functionality.