[Snyk] Security upgrade ubuntu from rolling to 21.10

[snyk-bot]

Keeping your Docker base image up-to-date means you’ll benefit from security fixes in the latest version of your chosen image.

Changes included in this PR

• Dockerfile

We recommend upgrading to ubuntu:21.10, as this image has only 12 known vulnerabilities. To do this, merge this pull request, then verify your application still works as expected.

Some of the most important vulnerabilities in your base image include:

Severity	Issue	Exploit Maturity
	Improper Verification of Cryptographic Signature SNYK-UBUNTU2110-PERL-1930909	No Known Exploit
	Time-of-check Time-of-use (TOCTOU) SNYK-UBUNTU2110-SHADOW-1758374	No Known Exploit
	Time-of-check Time-of-use (TOCTOU) SNYK-UBUNTU2110-SHADOW-1758374	No Known Exploit
	NULL Pointer Dereference SNYK-UBUNTU2110-TAR-1744334	No Known Exploit
	CVE-2018-25032 SNYK-UBUNTU2110-ZLIB-2433596	No Known Exploit

---

Note: You are seeing this because you or someone else with access to this repository has authorized Snyk to open fix PRs.

For more information:
🧐 View latest project report

🛠 Adjust project settings

---

Learn how to fix vulnerabilities with free interactive lessons:

🦉 Learn about vulnerability in an interactive lesson of Snyk Learn.