CVE-2021-31739Public exploitNetwork attack vector

Browser script execution via unencoded subject parameter

Published Nov 18, 2022 · Updated Apr 29, 2025

Reflected XSS in SEPPmail 11.1.10 allows remote attackers to execute JavaScript in a target's browser through a crafted subject URL. The web.app response places the subject query parameter into a hidden predefinedsubject input's value attribute without correct HTML encoding, allowing markup to escape the attribute. Exploitation requires the target to open the attacker-created URL and a bypass of the deployed content security policy; successful execution can expose credentials entered into attacker-controlled content.

CVSS severity6.1
Medium
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in SEPPmail 11.1.10 allows remote attackers to execute JavaScript in a target's browser through a crafted subject URL. The web.app response places the subject query parameter into a hidden predefinedsubject input's value attribute without correct HTML encoding, allowing markup to escape the attribute. Exploitation requires the target to open the attacker-created URL and a bypass of the deployed content security policy; successful execution can expose credentials entered into attacker-controlled content.

The record

CVE
CVE-2021-31739
Published
Nov 18, 2022
Updated
Apr 29, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 18, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 29, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1Pentagrid AGCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

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

Technologies

Your stack

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Your stack

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