CVE-2020-25739 Gon gem lack of escaping certain input when outputting as JSON

What is CVE-2020-25739?

CVE-2020-25739 is a medium-severity cross-site scripting vulnerability in Canonical Ubuntu Linux, published on 23 Sep 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

An issue was discovered in the gon gem before gon-6.4.0 for Ruby. MultiJson does not honor the escape_mode parameter to escape fields as an XSS protection mechanism. To mitigate, json_dumper.rb in gon now does escaping for XSS by default without relying on MultiJson.

Weakness: CWE-79

Which versions are affected by CVE-2020-25739?

2 open source packages ship an affected version, including gon. It affects 3 products.

Products include Canonical Ubuntu Linux, Debian Debian Linux, Gon Project Gon.

How do I fix CVE-2020-25739?

Upgrade gon to 6.4.0 or later.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2020-25739 being exploited?

There is no known exploitation of CVE-2020-25739 in the wild and no public exploit code.

Other vulnerabilities in Canonical Ubuntu Linux

• CVE-2020-11651 SaltStack Salt Authentication Bypass Exploited Critical 9.8
• CVE-2020-7247 OpenSMTPD Remote Code Execution Exploited Critical 9.8
• CVE-2019-16928 Exim Out-of-bounds Write Exploited Critical 9.8
• CVE-2018-6789 Exim Buffer Overflow Exploited Critical 9.8
• CVE-2015-2590 Oracle Java SE and Java SE Embedded Remote Code Execution Exploited Critical 9.8

All Canonical Ubuntu Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2020-25739, DLA-2380-1, GHSA-78vq-9j56-wrfr, UBUNTU-CVE-2020-25739, USN-4560-1.