CVE-2021-26813 markdown2 Regular Expression Denial of Service

What is CVE-2021-26813?

CVE-2021-26813 is a high-severity denial of service vulnerability in Fedoraproject Fedora, published on 3 Mar 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

markdown2 >=1.0.1.18, fixed in 2.4.0, is affected by a regular expression denial of service vulnerability. If an attacker provides a malicious string, it can make markdown2 processing difficult or delayed for an extended period of time.

Weakness: CWE-1333

Which versions are affected by CVE-2021-26813?

3 open source packages ship an affected version, including markdown2. It affects 2 products.

Products include Fedoraproject Fedora, Markdown2 Project Markdown2.

How do I fix CVE-2021-26813?

Upgrade markdown2 to 2.4.0 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-2021-26813 being exploited?

There is no known exploitation of CVE-2021-26813 in the wild and no public exploit code.

Other vulnerabilities in Fedoraproject Fedora

• CVE-2024-4577 PHP-CGI OS Command Injection Exploited Critical 9.8
• CVE-2021-39226 Grafana Authentication Bypass Exploited Critical 9.8
• CVE-2019-5544 VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow Exploited Critical 9.8
• CVE-2024-4947 Google Chromium V8 Type Confusion Exploited Critical 9.6
• CVE-2024-4671 Google Chromium Visuals Use-After-Free Exploited Critical 9.6

All Fedoraproject Fedora vulnerabilities

Sources

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

Also known as DEBIAN-CVE-2021-26813, GHSA-jr9p-r423-9m2r, PYSEC-2021-20, UBUNTU-CVE-2021-26813, openSUSE-SU-2021:0429-1, openSUSE-SU-2021:0451-1.