CVE-2023-35133: Moodle: ssrf risk due to insufficient check on the curl blocked hosts

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-06-22 · updated 2026-06-17
Weakness: CWE-918

Description

An issue in the logic used to check 0.0.0.0 against the cURL blocked hosts lists resulted in an SSRF risk. This flaw affects Moodle versions 4.2, 4.1 to 4.1.3, 4.0 to 4.0.8, 3.11 to 3.11.14, 3.9 to 3.9.21 and earlier unsupported versions.

Affected products

Moodle: before 3.9.22; from 3.11.0 before 3.11.15; from 4.0.0 before 4.0.9; from 4.1.0 before 4.1.4; 4.2.0 — fixed in 3.11.15, 3.9.22, 4.0.9, 4.1.4

How to fix

Upgrade to a fixed version: Moodle 3.11.15, 3.9.22, 4.0.9, 4.1.4. Check the vendor advisory for mitigations.

References

https://bugzilla.redhat.com/show_bug.cgi?id=2214373
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/7A72KX4WU6GK2CX4TKYFGFASPKOEOJFC/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I5QAEAGJ44NVXLAJFJXKARKC45OGEDXT/
https://moodle.org/mod/forum/discuss.php?d=447831
https://bugzilla.redhat.com/show_bug.cgi?id=2214373
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/7A72KX4WU6GK2CX4TKYFGFASPKOEOJFC/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I5QAEAGJ44NVXLAJFJXKARKC45OGEDXT/
https://moodle.org/mod/forum/discuss.php?d=447831

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