Debian Security Advisory

DLA-2695-1 klibc -- LTS security update

Date Reported:
28 Jun 2021
Affected Packages:
Security database references:
In the Debian bugtracking system: Bug 989505.
In Mitre's CVE dictionary: CVE-2021-31870, CVE-2021-31871, CVE-2021-31872, CVE-2021-31873.
More information:

Several vulnerabilities have been discovered in klibc. Depending on how klibc is used, these could lead to the execution of arbitrary code, privilege escalation, or denial of service.

Thanks to Microsoft Vulnerability Research for reporting the heap bugs and going some of the way to identifying the cpio bugs.

  • CVE-2021-31870

    Multiplication in the calloc() function may result in an integer overflow and a subsequent heap buffer overflow.

  • CVE-2021-31871

    An integer overflow in the cpio command may result in a NULL pointer dereference.

  • CVE-2021-31872

    Multiple possible integer overflows in the cpio command on 32-bit systems may result in a buffer overflow or other security impact.

  • CVE-2021-31873

    Additions in malloc() function may result in integer overflow and subsequent heap buffer overflow.

For Debian 9 stretch, these problems have been fixed in version 2.0.4-9+deb9u1.

We recommend that you upgrade your klibc packages.

For the detailed security status of klibc 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: