CVE-2026-56735

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Source

https://cve.org/CVERecord?id=CVE-2026-56735

Import Source

https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-56735.json

JSON Data

https://api.osv.dev/v1/vulns/CVE-2026-56735

Aliases

GHSA-7fwx-3xr4-qm6w

Published

2026-09-25T17:04:03Z

Modified

2026-09-27T03:47:27Z

Severity

5.3 (Medium) CVSS_V4 - CVSS: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 Calculator

Summary

Zammad: Improper neutralization of `srcset` attribute in IMG tags in Zammad

Details

Zammad is a web based open source helpdesk/customer support system. Prior to 7.0.2 and 7.1.0, zammad's HTML sanitizer (HtmlSanitizer::Strict) blocks external URLs in to prevent remote content loading, but the srcset attribute, also allowlisted for , is not subject to the same check. This oversight allows an attacker to embed arbitrary external URLs in the srcset attribute just by sending an e-mail, effectively bypassing the external content protection. When an agent views the ticket containing the malicious srcset, the browser will silently load the attacker-controlled URL, resulting in the leakage of the agent's IP address, User-Agent, Referer, and the exact time the ticket was viewed. HtmlSanitizer::Strict got extended to block external URLs in the srcset attribute of tags. This was done to prevent tracking pixels and external content loading, which could compromise user privacy. This issue is fixed in versions 7.0.2 and 7.1.0.

Database specific

{
    "cna_assigner":  "GitHub_M",
    "cwe_ids":  [
        "CWE-82"
    ],
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/56xxx/CVE-2026-56735.json"
}

References

Affected packages

Git / github.com/zammad/zammad

Affected ranges

Type

GIT

Repo

https://github.com/zammad/zammad

Events

Introduced

Fixed

02c1ff8dc65961352dc047013bece9dff1f2ffb7

Fixed

9dc15acf239dbc32ec357708859f2d86b188846c

Fixed

ecbb861ce33908e4b52bb2c78d816a0eef69e6a6

Database specific

Show details

{
    "extracted_events":  [
        {
            "introduced":  "0"
        },
        {
            "fixed":  "7.0.2"
        }
    ],
    "source":  [
        "AFFECTED_FIELD",
        "REFERENCES"
    ]
}

Affected versions

1.*

1.6.0

3.*

3.7.0

5.*

5.2.0-alpha

5.3.0-alpha

5.4.0-alpha

5.5.0-alpha

6.*

6.0.0-alpha

6.1.0-alpha

6.2.0-alpha

6.3.0-alpha

6.4.0-alpha

6.5.0-alpha

6.6.0-alpha

7.*

7.0.0

7.0.0-alpha

7.0.1

7.1.0-alpha

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-56735.json"