CVE-2026-56735Network attack vectorHinoki check available

Agent tracking via unchecked image srcset URLs

Published Sep 25, 2026 · Updated Sep 25, 2026

Information disclosure in Zammad 7.0.1 and earlier allows remote attackers to track agents by emailing a crafted image. HtmlSanitizer::Strict checks external URLs in an image's src attribute but leaves the allowlisted srcset attribute unchecked, so the browser loads an attacker-controlled URL. An agent must view the resulting ticket, which discloses the agent's IP address, User-Agent, Referer, and viewing time.

CVSS severity5.3
Medium
EPSS probability0.42%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Information disclosure in Zammad 7.0.1 and earlier allows remote attackers to track agents by emailing a crafted image. HtmlSanitizer::Strict checks external URLs in an image's src attribute but leaves the allowlisted srcset attribute unchecked, so the browser loads an attacker-controlled URL. An agent must view the resulting ticket, which discloses the agent's IP address, User-Agent, Referer, and viewing time.

The record

CVE
CVE-2026-56735
Published
Sep 25, 2026
Updated
Sep 25, 2026
Vendor
Zammad GmbH
Product
Zammad
Classifications
CWE-82, T1566
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 25, 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?

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

  1. Affected versionversion=< 7.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zammad GmbH · Zammadversion=< 7.0.2

Published CVSS scores

5.3Zammad via GitHub Security AdvisoryCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA: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.

Activity data is delayed. The latest report is Sep 28, 2026.

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

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-82Improper Neutralization of Script in Attributes of IMG Tags in a Web Page
T1566Phishing

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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