How severe is CVE-2021-31520?

CVE-2021-31520 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-31520 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-31520?

CVE-2021-31520 primarily affects Trendmicro Im Security. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-31520?

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-2021-31520 published?

CVE-2021-31520 was published on 2021-05-10 and last updated on 2026-06-17.

CVE-2021-31520

CVE-2021-31520 is a high-severity vulnerability in Trendmicro Im Security with a CVSS 3.x base score of 8.1. 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-287.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 6.8
EPSS exploit prediction: 4% (89th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-287
Affected product: Trendmicro Im Security
Published: 2021-05-10
Last modified: 2026-06-17

Description

A weak session token authentication bypass vulnerability in Trend Micro IM Security 1.6 and 1.6.5 could allow an remote attacker to guess currently logged-in administrators' session session token in order to gain access to the product's web management interface.

Frequently asked questions

What is CVE-2021-31520?: A weak session token authentication bypass vulnerability in Trend Micro IM Security 1.6 and 1.6.5 could allow an remote attacker to guess currently logged-in administrators' session session token in order to gain access to the product's web management interface.
How severe is CVE-2021-31520?: CVE-2021-31520 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-31520 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-31520?: CVE-2021-31520 primarily affects Trendmicro Im Security. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-31520?: 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-2021-31520 published?: CVE-2021-31520 was published on 2021-05-10 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:trendmicro:im_security:1.6:*:*:*:*:*:*:*
cpe:2.3:a:trendmicro:im_security:1.6.5:*:*:*:*:*:*:*

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