CVE-2026-9818
Roundcube Local/Private URL Fetch Bypass
Description
Roundcube's HTML sanitization path for message rendering allows loopback, localhost, RFC1918, link-local, and ULA URLs even when remote content loading is disabled. A remote attacker can send an HTML email that causes the victim's browser to issue requests to local or private-network services simply by opening the message preview.
INFO
Published Date :
May 28, 2026, 1:16 p.m.
Last Modified :
May 28, 2026, 1:16 p.m.
Remotely Exploit :
Yes !
Source :
6064c9f1-42e5-4cc5-a67a-1636d7a9d3fd
Affected Products
The following products are affected by CVE-2026-9818
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 3.1 | MEDIUM | 6064c9f1-42e5-4cc5-a67a-1636d7a9d3fd |
Solution
- Update Roundcube to the latest version.
- Configure stricter URL sanitization rules.
- Disable remote content loading if possible.
- Educate users about risky email content.
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-2026-9818.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-9818 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-2026-9818
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-2026-9818 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-9818 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.
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New CVE Received by 6064c9f1-42e5-4cc5-a67a-1636d7a9d3fd
May. 28, 2026
Action Type Old Value New Value Added Description Roundcube's HTML sanitization path for message rendering allows loopback, localhost, RFC1918, link-local, and ULA URLs even when remote content loading is disabled. A remote attacker can send an HTML email that causes the victim's browser to issue requests to local or private-network services simply by opening the message preview. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N Added CWE CWE-184 Added Reference https://advisories.orangecyberdefense.com/advisories/163 Added Reference https://github.com/roundcube/roundcubemail/commit/7b52353653a67e6073b97d70eb94047132b78556 Added Reference https://github.com/roundcube/roundcubemail/commit/faf867432f51ebbe100382a70a9e3c042415ee1b Added Reference https://github.com/roundcube/roundcubemail/releases/tag/1.6.16 Added Reference https://github.com/roundcube/roundcubemail/releases/tag/1.7.1