A NSS security update has been released for Ubuntu Linux 18.04 LTS, 20.04 LTS, 21.04, and 21.10.

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Ubuntu Security Notice USN-5168-1
December 01, 2021

nss vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.10
- Ubuntu 21.04
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

NSS could be made to crash or run programs if it verified a specially
crafted signature.

Software Description:
- nss: Network Security Service library

Details:

Tavis Ormandy discovered that NSS incorrectly handled verifying DSA/RSA-PSS
signatures. A remote attacker could use this issue to cause NSS to crash,
resulting in a denial of service, or possibly execute arbitrary code.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 21.10:
libnss3 2:3.68-1ubuntu1.1

Ubuntu 21.04:
libnss3 2:3.61-1ubuntu2.1

Ubuntu 20.04 LTS:
libnss3 2:3.49.1-1ubuntu1.6

Ubuntu 18.04 LTS:
libnss3 2:3.35-2ubuntu2.13

After a standard system update you need to restart any applications that
use NSS, such as Evolution, to make all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-5168-1
CVE-2021-43527

Package Information:
  https://launchpad.net/ubuntu/+source/nss/2:3.68-1ubuntu1.1
  https://launchpad.net/ubuntu/+source/nss/2:3.61-1ubuntu2.1
  https://launchpad.net/ubuntu/+source/nss/2:3.49.1-1ubuntu1.6
  https://launchpad.net/ubuntu/+source/nss/2:3.35-2ubuntu2.13