CVE-2026-72721
Discourse: Onebox Domain Blocklist Bypass via Case-Sensitive Comparison
Description
Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, Onebox::DomainChecker.is_blocked? compares hostnames and SiteSetting.blocked_onebox_domains entries case-sensitively, allowing an attacker to bypass configured Onebox domain restrictions by changing character casing in a redirect target hostname. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.
INFO
Published Date :
Aug. 10, 2026, 4:19 p.m.
Last Modified :
Aug. 10, 2026, 5:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-72721
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Discourse to version 2026.1.6 or later.
- Update Discourse to version 2026.5.2 or later.
- Update Discourse to version 2026.6.1 or later.
- Update Discourse to version 2026.7.0 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-72721.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-72721 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-72721
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-72721 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-72721 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 10, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-72721', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-10T16:58:55.983146Z'} -
New CVE Received by [email protected]
Aug. 10, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'discourse', 'product': 'discourse', 'versions': [{'status': 'affected', 'version': '< 2026.1.6'}, {'status': 'affected', 'version': '>= 2026.5.0-latest, < 2026.5.2'}, {'status': 'affected', 'version': '>= 2026.6.0-latest, < 2026.6.1'}, {'status': 'affected', 'version': '>= 2026.7.0-latest, < 2026.7.0'}]}] Added Description Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, Onebox::DomainChecker.is_blocked? compares hostnames and SiteSetting.blocked_onebox_domains entries case-sensitively, allowing an attacker to bypass configured Onebox domain restrictions by changing character casing in a redirect target hostname. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N Added CWE CWE-178 Added Reference https://github.com/discourse/discourse/commit/a3e10759fef47f03d450649bb51d9e84f4c68b8f Added Reference https://github.com/discourse/discourse/commit/c2eb6b0e5597d6f28f4be739b83300bc9c69e3cd Added Reference https://github.com/discourse/discourse/commit/caa615c371b1696982ee11ac8f3558f0f8ced584 Added Reference https://github.com/discourse/discourse/commit/f503971d311b7b0dfdb751ee8cfd67e8cb99f5c5 Added Reference https://github.com/discourse/discourse/pull/42091 Added Reference https://github.com/discourse/discourse/pull/42092 Added Reference https://github.com/discourse/discourse/pull/42093 Added Reference https://github.com/discourse/discourse/pull/42094 Added Reference https://github.com/discourse/discourse/security/advisories/GHSA-3x7x-24rq-h5j6