CVE-2026-42451 (GCVE-0-2026-42451)
Vulnerability from cvelistv5 – Published: 2026-05-08 22:51 – Updated: 2026-05-12 18:31
VLAI
EPSS
VEX
Title
Grimmory: Stored XSS via Malicious EPUB Enables Session Token Theft
Summary
Grimmory is a self-hosted digital library. Prior to version 2.3.1, a stored cross-site scripting (XSS) vulnerability in Grimmory's browser-based EPUB reader allows an attacker to embed arbitrary JavaScript in a crafted EPUB file. When a victim opens the book, the script executes in their browser with full access to the Grimmory application's session context. This can enable session token theft and account takeover, including administrative access if an administrator opens the affected book. This issue has been patched in version 2.3.1.
Severity
6.3 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-12 13:16 UTC
CWE
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/grimmory-tools/grimmory/securi… | x_refsource_CONFIRM |
| http://github.com/grimmory-tools/grimmory/release… | x_refsource_MISC |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| grimmory-tools | grimmory |
Affected:
< 2.3.1
|
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-42451",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-05-12T13:16:55.827303Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-05-12T18:31:26.652Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "grimmory",
"vendor": "grimmory-tools",
"versions": [
{
"status": "affected",
"version": "\u003c 2.3.1"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "Grimmory is a self-hosted digital library. Prior to version 2.3.1, a stored cross-site scripting (XSS) vulnerability in Grimmory\u0027s browser-based EPUB reader allows an attacker to embed arbitrary JavaScript in a crafted EPUB file. When a victim opens the book, the script executes in their browser with full access to the Grimmory application\u0027s session context. This can enable session token theft and account takeover, including administrative access if an administrator opens the affected book. This issue has been patched in version 2.3.1."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "HIGH",
"attackVector": "LOCAL",
"availabilityImpact": "LOW",
"baseScore": 6.3,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:L",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-79",
"description": "CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-80",
"description": "CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-08T22:51:21.920Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/grimmory-tools/grimmory/security/advisories/GHSA-frv6-5wq5-9p24",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/grimmory-tools/grimmory/security/advisories/GHSA-frv6-5wq5-9p24"
},
{
"name": "http://github.com/grimmory-tools/grimmory/releases/tag/v2.3.1",
"tags": [
"x_refsource_MISC"
],
"url": "http://github.com/grimmory-tools/grimmory/releases/tag/v2.3.1"
}
],
"source": {
"advisory": "GHSA-frv6-5wq5-9p24",
"discovery": "UNKNOWN"
},
"title": "Grimmory: Stored XSS via Malicious EPUB Enables Session Token Theft"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-42451",
"datePublished": "2026-05-08T22:51:21.920Z",
"dateReserved": "2026-04-27T13:55:58.693Z",
"dateUpdated": "2026-05-12T18:31:26.652Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-42451",
"date": "2026-08-30",
"epss": "0.00136",
"percentile": "0.03348"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-42451\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-05-08T23:16:38.680\",\"lastModified\":\"2026-07-24T21:10:00.143\",\"vulnStatus\":\"Deferred\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Grimmory is a self-hosted digital library. Prior to version 2.3.1, a stored cross-site scripting (XSS) vulnerability in Grimmory\u0027s browser-based EPUB reader allows an attacker to embed arbitrary JavaScript in a crafted EPUB file. When a victim opens the book, the script executes in their browser with full access to the Grimmory application\u0027s session context. This can enable session token theft and account takeover, including administrative access if an administrator opens the affected book. This issue has been patched in version 2.3.1.\"},{\"lang\":\"es\",\"value\":\"Grimmory es una biblioteca digital autoalojada. Antes de la versi\u00f3n 2.3.1, una vulnerabilidad de cross-site scripting (XSS) almacenado en el lector de EPUB basado en navegador de Grimmory permite a un atacante incrustar JavaScript arbitrario en un archivo EPUB manipulado. Cuando una v\u00edctima abre el libro, el script se ejecuta en su navegador con acceso completo al contexto de sesi\u00f3n de la aplicaci\u00f3n Grimmory. Esto puede permitir el robo de tokens de sesi\u00f3n y la toma de control de cuentas, incluyendo acceso administrativo si un administrador abre el libro afectado. Este problema ha sido parcheado en la versi\u00f3n 2.3.1.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"grimmory-tools\",\"product\":\"grimmory\",\"versions\":[{\"version\":\"\u003c 2.3.1\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:L\",\"baseScore\":6.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"REQUIRED\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":0.8,\"impactScore\":5.5}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-05-12T13:16:55.827303Z\",\"id\":\"CVE-2026-42451\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"total\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-79\"},{\"lang\":\"en\",\"value\":\"CWE-80\"}]}],\"references\":[{\"url\":\"http://github.com/grimmory-tools/grimmory/releases/tag/v2.3.1\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/grimmory-tools/grimmory/security/advisories/GHSA-frv6-5wq5-9p24\",\"source\":\"security-advisories@github.com\"}]}}",
"redhat_vex": {
"current_release_date": "2026-05-12T20:21:18+00:00",
"cve": "CVE-2026-42451",
"id": "CVE-2026-42451",
"initial_release_date": "2026-01-01T00:00:00+00:00",
"product_status:known_not_affected": "1",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "Grimmory: Stored XSS via Malicious EPUB Enables Session Token Theft",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42451.json",
"version": "3"
},
"vulnrichment": {
"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-42451\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-05-12T13:16:55.827303Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-05-12T13:17:29.405Z\"}}], \"cna\": {\"title\": \"Grimmory: Stored XSS via Malicious EPUB Enables Session Token Theft\", \"source\": {\"advisory\": \"GHSA-frv6-5wq5-9p24\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 6.3, \"attackVector\": \"LOCAL\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:L\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"REQUIRED\", \"attackComplexity\": \"HIGH\", \"availabilityImpact\": \"LOW\", \"privilegesRequired\": \"LOW\", \"confidentialityImpact\": \"HIGH\"}}], \"affected\": [{\"vendor\": \"grimmory-tools\", \"product\": \"grimmory\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003c 2.3.1\"}]}], \"references\": [{\"url\": \"https://github.com/grimmory-tools/grimmory/security/advisories/GHSA-frv6-5wq5-9p24\", \"name\": \"https://github.com/grimmory-tools/grimmory/security/advisories/GHSA-frv6-5wq5-9p24\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"http://github.com/grimmory-tools/grimmory/releases/tag/v2.3.1\", \"name\": \"http://github.com/grimmory-tools/grimmory/releases/tag/v2.3.1\", \"tags\": [\"x_refsource_MISC\"]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"Grimmory is a self-hosted digital library. Prior to version 2.3.1, a stored cross-site scripting (XSS) vulnerability in Grimmory\u0027s browser-based EPUB reader allows an attacker to embed arbitrary JavaScript in a crafted EPUB file. When a victim opens the book, the script executes in their browser with full access to the Grimmory application\u0027s session context. This can enable session token theft and account takeover, including administrative access if an administrator opens the affected book. This issue has been patched in version 2.3.1.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-79\", \"description\": \"CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)\"}]}, {\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-80\", \"description\": \"CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-05-08T22:51:21.920Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-42451\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-12T18:31:26.652Z\", \"dateReserved\": \"2026-04-27T13:55:58.693Z\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"datePublished\": \"2026-05-08T22:51:21.920Z\", \"assignerShortName\": \"GitHub_M\"}",
"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…
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.
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.
Loading…
Loading…