CVE-2023-34461: PyBB is an open source bulletin board. A manual code review of the PyBB bulletin board server has revealed that a vulnerability could have been exploi...

Description

PyBB is an open source bulletin board. A manual code review of the PyBB bulletin board server has revealed that a vulnerability could have been exploited in which users could submit any type of HTML tag, and have said tag run. For example, a malicious `<a>` that looks like ```<a href=javascript:alert (1)>xss</a>``` could have been used to run code through JavaScript on the client side. The problem has been patched as of commit `5defd92`, and users are advised to upgrade. Attackers do need posting privilege in order to exploit this vulnerability. This vulnerability is present within the 0.1.0 release, and users are advised to upgrade to 0.1.1. Users unable to upgrade may be able to work around the attack by either; Removing the ability to create posts, removing the `|safe` tag from the Jinja2 template titled "post.html" in templates or by adding manual validation of links in the post creation section.

Metrics

CVSS 3.1

5.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

0.34%

25.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Pybb Project	Pybb	0.1.0

References

https://github.com/benjjvi/PyBB/commit/5defd922ab05a193a783392d447c6538628cf854Patch
https://github.com/benjjvi/PyBB/security/advisories/GHSA-mv96-w49p-438pMitigation, Patch, Third Party Advisory
https://github.com/benjjvi/PyBB/commit/5defd922ab05a193a783392d447c6538628cf854Patch
https://github.com/benjjvi/PyBB/security/advisories/GHSA-mv96-w49p-438pMitigation, Patch, Third Party Advisory

Timeline

Published: Jun 19, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-34461?

PyBB is an open source bulletin board. A manual code review of the PyBB bulletin board server has revealed that a vulnerability could have been exploited in which users could submit any type of HTML tag, and have said tag run. For example, a malicious `<a>` that looks like ```<a href=javascript:alert (1)>xss</a>``` could have been used to run code through JavaScript on the client side. The problem has been patched as of commit `5defd92`, and users are advised to upgrade. Attackers do need posting privilege in order to exploit this vulnerability. This vulnerability is present within the 0.1.0 release, and users are advised to upgrade to 0.1.1. Users unable to upgrade may be able to work around the attack by either; Removing the ability to create posts, removing the `|safe` tag from the Jinja2 template titled "post.html" in templates or by adding manual validation of links in the post creation section.

How severe is CVE-2023-34461?

CVE-2023-34461 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.34% probability of exploitation in the next 30 days.

How do I fix CVE-2023-34461?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.