Debian Security Advisory

DLA-2713-1 linux -- LTS security update

Date Reported:
20 Jul 2021
Affected Packages:
Security database references:
In the Debian bugtracking system: Bug 990072.
In Mitre's CVE dictionary: CVE-2021-3609, CVE-2021-21781, CVE-2021-33909, CVE-2021-34693.
More information:

Brief introduction

  • CVE-2021-3609

    Norbert Slusarek reported a race condition vulnerability in the CAN BCM networking protocol, allowing a local attacker to escalate privileges.

  • CVE-2021-21781

    "Lilith>_>" of Cisco Talos discovered that the Arm initialisation code does not fully initialise the sigpage that is mapped into user-space processes to support signal handling. This could result in leaking sensitive information, particularly when the system is rebooted.

  • CVE-2021-33909

    The Qualys Research Labs discovered a size_t-to-int conversion vulnerability in the Linux kernel's filesystem layer. An unprivileged local attacker able to create, mount, and then delete a deep directory structure whose total path length exceeds 1GB, can take advantage of this flaw for privilege escalation.

    Details can be found in the Qualys advisory at

  • CVE-2021-34693

    Norbert Slusarek discovered an information leak in the CAN BCM networking protocol. A local attacker can take advantage of this flaw to obtain sensitive information from kernel stack memory.

For Debian 9 stretch, these problems have been fixed in version 4.9.272-2.

We recommend that you upgrade your linux packages.

For the detailed security status of linux please refer to its security tracker page at:

Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: