CVE-2026-29964Network attack vector

Arbitrary script execution via unencoded reflected input

Published May 18, 2026 · Updated May 18, 2026

Reflected XSS in HSC MailInspector 5.3.3-7 allows remote attackers to execute arbitrary JavaScript through /tap/tap.php. The endpoint places user-controlled input into its HTTP response without context-appropriate output encoding, including alternate or obfuscated script syntax. Exploitation requires a victim to follow a crafted request, after which the script acts with that victim's browser-session access.

CVSS severity6.1
Medium
EPSS probability0.24%
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 HSC MailInspector 5.3.3-7 allows remote attackers to execute arbitrary JavaScript through /tap/tap.php. The endpoint places user-controlled input into its HTTP response without context-appropriate output encoding, including alternate or obfuscated script syntax. Exploitation requires a victim to follow a crafted request, after which the script acts with that victim's browser-session access.

The record

CVE
CVE-2026-29964
Published
May 18, 2026
Updated
May 18, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, CWE-87, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 18, 2026CVE publishedPublication date reported by the CVE source.
  2. May 18, 2026Record 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

8.2sql3t0CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-87Improper Neutralization of Alternate XSS Syntax
T1203Exploitation for Client Execution

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

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Your stack

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