CVE-2025-53021

A session fixation vulnerability in Moodle 3.x through 3.11.18 allows unauthenticated attackers to hijack user sessions via the sesskey parameter. The sesskey can be obtained without authentication and reused within the OAuth2 login flow, resulting in the victim's session being linked to the attacker's. Successful exploitation results in full account takeover. According to the Moodle Releases page, "Bug fixes for security issues in 3.11.x ended 11 December 2023." NOTE: This vulnerability only affects products that are no longer supported by the maintainer.

Published: 2025-06-24 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-53021 is rated Low Risk (22.6/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.26%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-53021

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.49% 0.26% -0.22%
2 2026-04-20 0.27% 0.49% +0.22%
3 2026-03-20 — 0.27% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-53021

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.2 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 1.6 2.5 [email protected]

Weakness enumeration for CVE-2025-53021

GitHub Security Advisory for CVE-2025-53021

GHSA-cgvv-3455-824j · Severity: medium · Ecosystem: composer — Moodle Session Fixation allows unauthenticated users to hijack sessions via sesskey parameter

OS Trackers for CVE-2025-53021

vendor priority summary link
ubuntu medium CVE-2025-53021 medium priority: Ubuntu including 1 source packages (moodle), 8 status rows across 8 suites (bionic, jammy, noble, oracular, plucky, questing, upstream, xenial): DNE 5, needs-triage 3. https://ubuntu.com/security/CVE-2025-53021

Affected software / configurations for CVE-2025-53021

Vendor Product Version Raw CPE
moodle moodle >= 3.0.0, <= 3.11.18 cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*

References for CVE-2025-53021

cvelogic Threat Intelligence