How severe is CVE-2021-3337?

CVE-2021-3337 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-3337 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 11% (95th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3337?

CVE-2021-3337 affects Hide Thread Content Project Hide Thread Content. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3337?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-3337 published?

CVE-2021-3337 was published on 2021-01-28 and last updated on 2026-06-17.

CVE-2021-3337

CVE-2021-3337 is a high-severity vulnerability in Hide Thread Content Project Hide Thread Content with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 11% places it in the 95th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-863.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 11% (95th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Hide Thread Content Project Hide Thread Content
Published: 2021-01-28
Last modified: 2026-06-17

Description

The Hide-Thread-Content plugin through 2021-01-27 for MyBB allows remote attackers to bypass intended content-reading restrictions by clicking on reply or quote in the postbit.

Frequently asked questions

What is CVE-2021-3337?: The Hide-Thread-Content plugin through 2021-01-27 for MyBB allows remote attackers to bypass intended content-reading restrictions by clicking on reply or quote in the postbit.
How severe is CVE-2021-3337?: CVE-2021-3337 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-3337 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 11% (95th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3337?: CVE-2021-3337 affects Hide Thread Content Project Hide Thread Content. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3337?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-3337 published?: CVE-2021-3337 was published on 2021-01-28 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:hide_thread_content_project:hide_thread_content:1.0:*:*:*:*:mybb:*:*

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