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Debian LTS Advisory DLA-2713-1                [email protected]
https://www.debian.org/lts/security/                        Ben Hutchings
July 20, 2021                                 https://wiki.debian.org/LTS
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Package        : linux
Version        : 4.9.272-2
CVE ID         : CVE-2021-3609 CVE-2021-21781 CVE-2021-33909 CVE-2021-34693
Debian Bug     : 990072

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
    https://www.qualys.com/2021/07/20/cve-2021-33909/sequoia-local-privilege-escalation-linux.txt

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:
https://security-tracker.debian.org/tracker/linux

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

--
Ben Hutchings - Debian developer, member of kernel, installer and LTS teams