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Fencer Vulns
medium 4.6

CVE-2023-34461 json

Cross-site Scripting (XSS) Availability in PyBB

published 2023-06-19 3 y ago modified 2026-06-17 4 mo ago also EUVD-2023-38525

cvss
4.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits
0
none known

Summary

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.

Patch / fix

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
22 mo ago

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.6 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
NVD 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Affected products

  • benjjvi PyBB

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.