CVE-2026-56735 (GCVE-0-2026-56735)
Vulnerability from cvelistv5 – Published: 2026-09-25 17:04 – Updated: 2026-09-25 19:06
VLAI
EPSS
VEX
Title
Zammad: Improper neutralization of `srcset` attribute in IMG tags in Zammad
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.
Severity
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
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
{
"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",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-56735",
"date": "2026-09-28",
"epss": "0.00421",
"percentile": "0.33947"
},
"nvd": {
"cve": {
"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"
}
]
}
},
"vulnrichment": {
"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": "2026-09-25T19:06:31.902Z",
"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"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
Loading…
Loading…
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.
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.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
Loading…