CVE-2020-5238 Denial of service in table parsing in cmark-gfm

What is CVE-2020-5238?

CVE-2020-5238 is a medium-severity denial of service vulnerability in Fedoraproject Fedora, published on 1 Jul 2020. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

The table extension in GitHub Flavored Markdown before version 0.29.0.gfm.1 takes O(n * n) time to parse certain inputs. An attacker could craft a markdown table which would take an unreasonably long time to process, causing a denial of service. This issue does not affect the upstream cmark project. The issue has been fixed in version 0.29.0.gfm.1.

Weakness: CWE-20

Which versions are affected by CVE-2020-5238?

1 open source package ship an affected version, including commonmark. It affects 2 products.

Products include Fedoraproject Fedora, Github Flavored Markdown Project Github Flavored Markdown.

How do I fix CVE-2020-5238?

Upgrade commonmark to 1.8 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2020-5238 being exploited?

There is no known exploitation of CVE-2020-5238 in the wild and no public exploit code.

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All Fedoraproject Fedora vulnerabilities

Sources

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

Also known as ALSA-2021:1972, DEBIAN-CVE-2020-5238, GHSA-7gc6-9qr5-hc85, RHSA-2021:1972, RSEC-2023-6, UBUNTU-CVE-2020-5238.