CVE-2023-23621 Discourse vulnerable to ReDoS in user agent parsing

What is CVE-2023-23621?

CVE-2023-23621 is a high-severity denial of service vulnerability in Discourse Discourse, published on 27 Jan 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Discourse is an open-source discussion platform. Prior to version 3.0.1 on the `stable` branch and version 3.1.0.beta2 on the `beta` and `tests-passed` branches, a malicious user can cause a regular expression denial of service using a carefully crafted user agent. This issue is patched in version 3.0.1 on the `stable` branch and version 3.1.0.beta2 on the `beta` and `tests-passed` branches. There are no known workarounds.

Weakness: CWE-1333

Which versions are affected by CVE-2023-23621?

1 open source package ship an affected version, including discourse. It affects 1 product.

Products include Discourse Discourse.

How do I fix CVE-2023-23621?

Upgrade discourse to 3.0.1 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-2023-23621 being exploited?

There is no known exploitation of CVE-2023-23621 in the wild and no public exploit code.

Other vulnerabilities in Discourse Discourse

• CVE-2021-41163 RCE via malicious SNS subscription payload Critical 10.0
• CVE-2022-36066 Discourse vulnerable to RCE via admins uploading maliciously zipped file Critical 9.1
• CVE-2022-39356 Discourse user account takeover via email and invite link High 8.9
• CVE-2023-22468 Discourse vulnerable to Cross-site Scripting in local oneboxes High 8.8
• CVE-2026-27934 Discourse leaks private topic title and post excerpt via user action API endpoint High 8.7

All Discourse Discourse vulnerabilities

Sources

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

Also known as BIT-discourse-2023-23621, GHSA-mrfp-54hf-jrcv.