CVE-2025-59526Network attack vector

HTML injection via newline-spanning tag bypass

Published Sep 22, 2025 · Updated Sep 22, 2025

HTML injection in Mailgen before 2.0.30 allows remote attackers to place HTML in plaintext email output through user-generated content. generatePlaintext removes tags with a single-line regular expression, so newline-spanning tags survive before the method decodes HTML entities. Exploitation requires a consuming project to pass attacker-influenced fields to this method; the result can alter generated email content, while downstream effects depend on how that output is rendered.

CVSS severity5.3
Medium
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTML injection in Mailgen before 2.0.30 allows remote attackers to place HTML in plaintext email output through user-generated content. generatePlaintext removes tags with a single-line regular expression, so newline-spanning tags survive before the method decodes HTML entities. Exploitation requires a consuming project to pass attacker-influenced fields to this method; the result can alter generated email content, while downstream effects depend on how that output is rendered.

The record

CVE
CVE-2025-59526
Published
Sep 22, 2025
Updated
Sep 22, 2025
Vendor
Elad Nava
Product
Mailgen
Classifications
CWE-79
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 22, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 22, 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?

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

  1. Affected versionversion=< 2.0.30

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Elad Nava · Mailgenversion=< 2.0.30

Published CVSS scores

5.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
2.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:L/E:U

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.

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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')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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