CVE-2026-87929 (GCVE-0-2026-87929)
Vulnerability from cvelistv5 – Published: 2026-09-09 16:45 – Updated: 2026-09-09 16:45 X_Open Source Unsupported When Assigned
VLAI
EPSS
VEX
Title
MaxSite CMS through 109.6 Authentication Bypass via Hardcoded Encryption Key
Summary
MaxSite CMS through 109.6 ships with a hardcoded session encryption key in application/config/config.php that is never changed during installation, allowing unauthenticated attackers to forge administrator session cookies. Attackers can mint a malicious ci_session cookie with administrator privileges by computing an HMAC-SHA1 using the publicly known encryption key, bypassing authentication checks in is_login() and mso_check_allow() functions.
Severity
9.8 (Critical)
CWE
- CWE-321 - Use of Hard-coded Cryptographic Key
Assigner
References
5 references
| URL | Tags |
|---|---|
| https://github.com/maxsite/cms | product |
| https://github.com/EviL0rd/maxsite-cve4/blob/main… | exploittechnical-description |
| https://github.com/maxsite/cms/blob/2ca0a0c7d1d71… | technical-description |
| https://github.com/maxsite/cms/blob/2ca0a0c7d1d71… | technical-description |
| https://www.vulncheck.com/advisories/maxsite-cms-… | third-party-advisory |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| MaxSite | MaxSite CMS |
Affected:
0.78 , ≤ 109.6
(custom)
cpe:2.3:a:max-3000:maxsite_cms:*:*:*:*:*:*:*:* |
Date Public
2026-09-09 00:00
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"packageURL": "pkg:github/maxsite/cms",
"product": "MaxSite CMS",
"repo": "https://github.com/maxsite/cms",
"vendor": "MaxSite",
"versions": [
{
"lessThanOrEqual": "109.6",
"status": "affected",
"version": "0.78",
"versionType": "custom"
}
]
}
],
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"vulnerable": true
}
],
"negate": false,
"operator": "OR"
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"credits": [
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"type": "reporter",
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{
"lang": "en",
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}
],
"metrics": [
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"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 9.3,
"baseSeverity": "CRITICAL",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
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"problemTypes": [
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"descriptions": [
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"description": "Use of Hard-coded Cryptographic Key",
"lang": "en",
"type": "CWE"
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"providerMetadata": {
"dateUpdated": "2026-09-09T16:45:00.096Z",
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{
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},
{
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},
{
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"tags": [
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],
"url": "https://www.vulncheck.com/advisories/maxsite-cms-through-109.6-authentication-bypass-via-hardcoded-encryption-key"
}
],
"source": {
"discovery": "EXTERNAL"
},
"tags": [
"x_open-source",
"unsupported-when-assigned"
],
"title": "MaxSite CMS through 109.6 Authentication Bypass via Hardcoded Encryption Key",
"x_generator": {
"engine": "vulncheck-endgame"
}
}
},
"cveMetadata": {
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"cveId": "CVE-2026-87929",
"datePublished": "2026-09-09T16:45:00.096Z",
"dateReserved": "2026-09-09T16:12:31.422Z",
"dateUpdated": "2026-09-09T16:45:00.096Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-87929",
"date": "2026-09-10",
"epss": "0.00288",
"percentile": "0.21131"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-87929\",\"sourceIdentifier\":\"disclosure@vulncheck.com\",\"published\":\"2026-09-09T17:17:53.840\",\"lastModified\":\"2026-09-09T20:14:00.420\",\"vulnStatus\":\"Deferred\",\"cveTags\":[{\"sourceIdentifier\":\"disclosure@vulncheck.com\",\"tags\":[\"unsupported-when-assigned\"]}],\"descriptions\":[{\"lang\":\"en\",\"value\":\"MaxSite CMS through 109.6 ships with a hardcoded session encryption key in application/config/config.php that is never changed during installation, allowing unauthenticated attackers to forge administrator session cookies. Attackers can mint a malicious ci_session cookie with administrator privileges by computing an HMAC-SHA1 using the publicly known encryption key, bypassing authentication checks in is_login() and mso_check_allow() functions.\"}],\"affected\":[{\"source\":\"disclosure@vulncheck.com\",\"affectedData\":[{\"vendor\":\"MaxSite\",\"product\":\"MaxSite CMS\",\"defaultStatus\":\"unaffected\",\"repo\":\"https://github.com/maxsite/cms\",\"packageURL\":\"pkg:github/maxsite/cms\",\"versions\":[{\"version\":\"0.78\",\"lessThanOrEqual\":\"109.6\",\"versionType\":\"custom\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"disclosure@vulncheck.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/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\",\"baseScore\":9.3,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"NONE\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"vulnConfidentialityImpact\":\"HIGH\",\"vulnIntegrityImpact\":\"HIGH\",\"vulnAvailabilityImpact\":\"HIGH\",\"subConfidentialityImpact\":\"NONE\",\"subIntegrityImpact\":\"NONE\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}],\"cvssMetricV31\":[{\"source\":\"disclosure@vulncheck.com\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"weaknesses\":[{\"source\":\"disclosure@vulncheck.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-321\"}]}],\"references\":[{\"url\":\"https://github.com/EviL0rd/maxsite-cve4/blob/main/2026.09.08-maxsite-cms-hardcoded-session-key-auth-bypass.md\",\"source\":\"disclosure@vulncheck.com\"},{\"url\":\"https://github.com/maxsite/cms\",\"source\":\"disclosure@vulncheck.com\"},{\"url\":\"https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/config/config.php#L230-L254\",\"source\":\"disclosure@vulncheck.com\"},{\"url\":\"https://github.com/maxsite/cms/blob/2ca0a0c7d1d71106a25dbb0f2aedaaefbf12802c/application/maxsite/common/core/init.php#L70-L96\",\"source\":\"disclosure@vulncheck.com\"},{\"url\":\"https://www.vulncheck.com/advisories/maxsite-cms-through-109.6-authentication-bypass-via-hardcoded-encryption-key\",\"source\":\"disclosure@vulncheck.com\"}]}}"
}
}
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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.
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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.
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.
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