How severe is CVE-2018-1000503?

CVE-2018-1000503 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2018-1000503 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-1000503?

CVE-2018-1000503 affects Mybb. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2018-1000503?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2018-1000503 published?

CVE-2018-1000503 was published on 2018-06-26 and last updated on 2026-06-17.

CVE-2018-1000503

CVE-2018-1000503 is a medium-severity vulnerability in Mybb with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-269.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
CVSS v2: 4.0
EPSS exploit prediction: 1% (46th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-269
Affected product: Mybb
Published: 2018-06-26
Last modified: 2026-06-17

Description

MyBB Group MyBB contains a Incorrect Access Control vulnerability in Private forums that can result in Users can view posts from private forums without having the password. This attack appear to be exploitable via Subscribe to a forum through IDOR. This vulnerability appears to have been fixed in 1.8.15.

Frequently asked questions

What is CVE-2018-1000503?: MyBB Group MyBB contains a Incorrect Access Control vulnerability in Private forums that can result in Users can view posts from private forums without having the password. This attack appear to be exploitable via Subscribe to a forum through IDOR. This vulnerability appears to have been fixed in 1.8.15.
How severe is CVE-2018-1000503?: CVE-2018-1000503 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2018-1000503 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-1000503?: CVE-2018-1000503 affects Mybb. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2018-1000503?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2018-1000503 published?: CVE-2018-1000503 was published on 2018-06-26 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mybb:mybb:*:*:*:*:*:*:*:*

More vulnerabilities in Mybb

CVE-2015-8974 — Critical (CVSS 10.0): SQL injection vulnerability in the Group Promotions module in the admin control panel in MyBB (aka MyBulletinBoard)…
CVE-2015-2786 — Critical (CVSS 10.0): Unspecified vulnerability in MyBB (aka MyBulletinBoard) before 1.8.4 has unknown attack vectors related to "Group join…
CVE-2011-5133 — Critical (CVSS 10.0): Unspecified vulnerability in MyBB before 1.6.5 has unknown impact and attack vectors, related to an "unparsed user…
CVE-2006-0218 — Critical (CVSS 10.0): Multiple unspecified vulnerabilities in MyBulletinBoard (MyBB) before 1.0.2 have unspecified impact and attack vectors,…
CVE-2011-10018 — Critical (CVSS 9.8): myBB version 1.6.4 was distributed with an unauthorized backdoor embedded in the source code. The backdoor allowed…
CVE-2020-22612 — Critical (CVSS 9.8): Installer RCE on settings file write in MyBB before 1.8.22.

All CVEs affecting Mybb →

Other CWE-269 (Improper Privilege Management) vulnerabilities

CVE-2026-31852 — Critical (CVSS 10.0): Jellyfin is an open-source media system. The code-quality.yml GitHub Actions workflow in jellyfin/jellyfin-ios is…
CVE-2025-20282 — Critical (CVSS 10.0): A vulnerability in an internal API of Cisco ISE and Cisco ISE-PIC could allow an unauthenticated, remote attacker to…
CVE-2025-0505 — Critical (CVSS 10.0): On Arista CloudVision systems (virtual or physical on-premise deployments), Zero Touch Provisioning can be used to gain…
CVE-2023-48418 — Critical (CVSS 10.0): In checkDebuggingDisallowed of DeviceVersionFragment.java, there is a possible way to access adb before SUW…
CVE-2023-48419 — Critical (CVSS 10.0): An attacker in the wifi vicinity of a target Google Home can spy on the victim, resulting in Elevation of Privilege
CVE-2023-31273 — Critical (CVSS 10.0): Protection mechanism failure in some Intel DCM software before version 5.2 may allow an unauthenticated user to…

Browse all CWE-269 (Improper Privilege Management) vulnerabilities →