CVE-2021-31520Network attack vector

Authentication bypass via guessable session tokens

Published May 10, 2021 · Updated Aug 3, 2024

Weak session-token authentication in Trend Micro IM Security 1.6 and 1.6.5 allows remote attackers to access the web management interface. The web console on TCP port 16373 uses guessable session tokens and accepts a valid guess as the currently logged-in administrator. Exploitation requires network access to the console and an active administrator session; a successful guess grants that session's console access.

CVSS severity7.3
High
EPSS probability3.90%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Weak session-token authentication in Trend Micro IM Security 1.6 and 1.6.5 allows remote attackers to access the web management interface. The web console on TCP port 16373 uses guessable session tokens and accepts a valid guess as the currently logged-in administrator. Exploitation requires network access to the console and an active administrator session; a successful guess grants that session's console access.

The record

CVE
CVE-2021-31520
Published
May 10, 2021
Updated
Aug 3, 2024
Vendor
Trend Micro
Product
Trend Micro IM Security
Classifications
CWE-287, T1550.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.6, 1.6.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Trend Micro · Trend Micro IM Securityversion=1.6, 1.6.5

Published CVSS scores

7.3Trend MicroCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
8.1NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1550.004Use Alternate Authentication Material: Web Session Cookie

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo