Vulnerability-Lookup

FKIE_CVE-2026-56735

Vulnerability from fkie_nvd - Published: 2026-09-25 18:17 - Updated: 2026-09-28 14:45

Severity

5.3 (Medium) - 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

Summary

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.

References

	URL	Tags
	security-advisories@github.com	https://github.com/zammad/zammad/commit/02c1ff8dc65961352dc047013bece9dff1f2ffb7
	security-advisories@github.com	https://github.com/zammad/zammad/releases/tag/7.0.2
	security-advisories@github.com	https://github.com/zammad/zammad/releases/tag/7.1.0
	security-advisories@github.com	https://github.com/zammad/zammad/security/advisories/GHSA-7fwx-3xr4-qm6w

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "zammad",
          "vendor": "zammad",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 7.0.2"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Zammad is a web based open source helpdesk/customer support system. Prior to 7.0.2 and 7.1.0, zammad\u0027s 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\u0027s 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."
    }
  ],
  "id": "CVE-2026-56735",
  "lastModified": "2026-09-28T14:45:39.697",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "PASSIVE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "LOW",
          "vulnIntegrityImpact": "LOW",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-56735",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-25T19:06:28.516570Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-25T18:17:28.880",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/zammad/zammad/commit/02c1ff8dc65961352dc047013bece9dff1f2ffb7"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/zammad/zammad/releases/tag/7.0.2"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/zammad/zammad/releases/tag/7.1.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/zammad/zammad/security/advisories/GHSA-7fwx-3xr4-qm6w"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-82"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

CVE-2026-56735 (GCVE-0-2026-56735)

Vulnerability from cvelistv5 – Published: 2026-09-25 17:04 – Updated: 2026-09-25 19:06

Title

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

Summary

Severity

5.3 (Medium)


                        
                          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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-25 19:06 UTC

CWE

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

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7712 records in the last 180 days details

References

4 references

URL	Tags
https://github.com/zammad/zammad/security/advisor…	x_refsource_CONFIRM
https://github.com/zammad/zammad/commit/02c1ff8dc…	x_refsource_MISC
https://github.com/zammad/zammad/releases/tag/7.0.2	x_refsource_MISC
https://github.com/zammad/zammad/releases/tag/7.1.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
zammad	zammad	Affected: < 7.0.2

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-56735",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-25T19:06:28.516570Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-25T19:06:35.154Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "zammad",
          "vendor": "zammad",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 7.0.2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Zammad is a web based open source helpdesk/customer support system. Prior to 7.0.2 and 7.1.0, zammad\u0027s 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\u0027s 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."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "PASSIVE",
            "vectorString": "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "LOW",
            "vulnIntegrityImpact": "LOW"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-82",
              "description": "CWE-82: Improper Neutralization of Script in Attributes of IMG Tags in a Web Page",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T17:04:03.247Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/zammad/zammad/security/advisories/GHSA-7fwx-3xr4-qm6w",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/zammad/zammad/security/advisories/GHSA-7fwx-3xr4-qm6w"
        },
        {
          "name": "https://github.com/zammad/zammad/commit/02c1ff8dc65961352dc047013bece9dff1f2ffb7",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/zammad/zammad/commit/02c1ff8dc65961352dc047013bece9dff1f2ffb7"
        },
        {
          "name": "https://github.com/zammad/zammad/releases/tag/7.0.2",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/zammad/zammad/releases/tag/7.0.2"
        },
        {
          "name": "https://github.com/zammad/zammad/releases/tag/7.1.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/zammad/zammad/releases/tag/7.1.0"
        }
      ],
      "source": {
        "advisory": "GHSA-7fwx-3xr4-qm6w",
        "discovery": "UNKNOWN"
      },
      "title": "Zammad: Improper neutralization of `srcset` attribute in IMG tags in Zammad"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-56735",
    "datePublished": "2026-09-25T17:04:03.247Z",
    "dateReserved": "2026-06-22T19:17:28.959Z",
    "dateUpdated": "2026-09-25T19:06:35.154Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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