CVE-2026-121880 (GCVE-0-2026-121880)
Vulnerability from cvelistv5 – Published: 2026-11-06 15:10 – Updated: 2026-11-06 17:45
VLAI
EPSS
VEX
Title
RStudio Server / Posit Workbench localhost port-proxy does not enforce per-session port ownership
Summary
Authorization bypass through user-controlled key in the localhost port-proxy (/p/<token>/) in Posit Software, PBC RStudio Server and Posit Workbench before 2026.08.0 allows remote authenticated users to reach web applications and other services bound to 127.0.0.1 under a different user's session, and to view their live rendered content and data, via a proxy URL constructed from the attacker's own port token for an arbitrary port number. The port token is a documented obfuscation measure and not an authorization boundary, and the proxy does not verify that the requested port belongs to the requesting user's session.
NOTE: exploitation requires an authenticated account on the same multi-user server and a target service listening on localhost at the time of access. Impact may be greater on hosts that co-locate additional privileged localhost services, and the bypass is not prevented by allow-shell=false; no setting restricts the port-proxy without disabling all application proxying.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-11-06 17:21 UTC
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://docs.posit.co/ide/news/#rstudio-2026.08.0 | release-notesvendor-advisory |
| https://trust.posit.co/updates | vendor-advisory |
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Posit Software, PBC | Posit Workbench |
Affected:
0 , < 2026.08.0
(custom)
cpe:2.3:a:posit:workbench:*:*:*:*:*:*:*:* |
||
| Posit Software, PBC | RStudio Server |
Affected:
0 , < 2026.08.0
(custom)
cpe:2.3:a:posit:rstudio_server:*:*:*:*:*:*:*:* |
Date Public
2026-11-04 11:03
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-121880",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-11-06T17:21:05.517519Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-11-06T17:45:27.737Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://posit.co/download/rstudio-server-pro/",
"cpes": [
"cpe:2.3:a:posit:workbench:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"localhost port-proxy (/p/\u003ctoken\u003e/)"
],
"platforms": [
"Linux"
],
"product": "Posit Workbench",
"programFiles": [
"src/cpp/core/http/UrlPorts.cpp"
],
"vendor": "Posit Software, PBC",
"versions": [
{
"lessThan": "2026.08.0",
"status": "affected",
"version": "0",
"versionType": "custom"
}
]
},
{
"collectionURL": "https://posit.co/download/rstudio-server/",
"cpes": [
"cpe:2.3:a:posit:rstudio_server:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"localhost port-proxy (/p/\u003ctoken\u003e/)"
],
"platforms": [
"Linux"
],
"product": "RStudio Server",
"programFiles": [
"src/cpp/core/http/UrlPorts.cpp"
],
"vendor": "Posit Software, PBC",
"versions": [
{
"lessThan": "2026.08.0",
"status": "affected",
"version": "0",
"versionType": "custom"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAffects multi-user RStudio Server / Posit Workbench deployments in which more than one user has an interactive session on the same host and application proxying via the localhost port-proxy is enabled (the default).\u0026nbsp;\u003c/p\u003e"
}
],
"value": "Affects multi-user RStudio Server / Posit Workbench deployments in which more than one user has an interactive session on the same host and application proxying via the localhost port-proxy is enabled (the default)."
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Luiz Felipe Mol (confu53)"
}
],
"datePublic": "2026-11-04T11:03:00.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAuthorization bypass through user-controlled key in the localhost port-proxy (\u003ccode\u003e/p/\u0026lt;token\u0026gt;/\u003c/code\u003e) in Posit Software, PBC RStudio Server and Posit Workbench before 2026.08.0 allows remote authenticated users to reach web applications and other services bound to 127.0.0.1 under a different user\u0027s session, and to view their live rendered content and data, via a proxy URL constructed from the attacker\u0027s own port token for an arbitrary port number. The port token is a documented obfuscation measure and not an authorization boundary, and the proxy does not verify that the requested port belongs to the requesting user\u0027s session.\u003c/p\u003e\u003cp\u003eNOTE: exploitation requires an authenticated account on the same multi-user server and a target service listening on localhost at the time of access. Impact may be greater on hosts that co-locate additional privileged localhost services, and the bypass is not prevented by \u003ccode\u003eallow-shell=false\u003c/code\u003e; no setting restricts the port-proxy without disabling all application proxying.\u003c/p\u003e"
}
],
"value": "Authorization bypass through user-controlled key in the localhost port-proxy (/p/\u003ctoken\u003e/) in Posit Software, PBC RStudio Server and Posit Workbench before 2026.08.0 allows remote authenticated users to reach web applications and other services bound to 127.0.0.1 under a different user\u0027s session, and to view their live rendered content and data, via a proxy URL constructed from the attacker\u0027s own port token for an arbitrary port number. The port token is a documented obfuscation measure and not an authorization boundary, and the proxy does not verify that the requested port belongs to the requesting user\u0027s session.\n\n\n\nNOTE: exploitation requires an authenticated account on the same multi-user server and a target service listening on localhost at the time of access. Impact may be greater on hosts that co-locate additional privileged localhost services, and the bypass is not prevented by allow-shell=false; no setting restricts the port-proxy without disabling all application proxying."
}
],
"impacts": [
{
"descriptions": [
{
"lang": "en",
"value": "Information disclosure: an authenticated user can view another user\u0027s running application and the data it renders. Where other network services are bound to localhost on the same host, those services may also become reachable through the proxy, and the potential impact in those deployments depends on what is running and how it is configured."
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "YES",
"Recovery": "AUTOMATIC",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"baseScore": 4.7,
"baseSeverity": "MEDIUM",
"exploitMaturity": "PROOF_OF_CONCEPT",
"privilegesRequired": "LOW",
"providerUrgency": "AMBER",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "DIFFUSE",
"vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:P/AU:Y/R:A/V:D/RE:M/U:Amber",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "MODERATE"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-639",
"description": "CWE-639 Authorization Bypass Through User-Controlled Key",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-862",
"description": "CWE-862 Missing Authorization",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-11-06T15:12:38.657Z",
"orgId": "8c484e69-127d-402b-9cdb-5f86ef43eb86",
"shortName": "POSIT"
},
"references": [
{
"name": "RStudio IDE / RStudio Server release notes",
"tags": [
"release-notes",
"vendor-advisory"
],
"url": "https://docs.posit.co/ide/news/#rstudio-2026.08.0"
},
{
"tags": [
"vendor-advisory"
],
"url": "https://trust.posit.co/updates"
}
],
"solutions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eUpgrade to Posit Workbench 2026.08.0 or later, or RStudio Server 2026.08.0 or later. The patched releases verify that a port requested through the localhost port-proxy belongs to the requesting user\u0027s session.\u003c/p\u003e"
}
],
"value": "Upgrade to Posit Workbench 2026.08.0 or later, or RStudio Server 2026.08.0 or later. The patched releases verify that a port requested through the localhost port-proxy belongs to the requesting user\u0027s session."
}
],
"source": {
"discovery": "EXTERNAL"
},
"timeline": [
{
"lang": "en",
"time": "2026-05-22T00:00:00.000Z",
"value": "Reported to Posit through coordinated disclosure"
},
{
"lang": "en",
"time": "2026-05-22T00:00:00.000Z",
"value": "Reproduced internally with a working proof of concept against Posit Workbench 2025.09"
},
{
"lang": "en",
"time": "2026-07-22T00:00:00.000Z",
"value": "CVE submission and security advisory approved by Posit"
}
],
"title": "RStudio Server / Posit Workbench localhost port-proxy does not enforce per-session port ownership",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eUntil the patched release is applied, operators of multi-user instances can reduce exposure by separating sensitive workloads onto dedicated hosts or per-user isolated environments rather than sharing a single multi-user node; avoiding co-location of sensitive network services on hosts that also run user sessions; and limiting shared-server access to mutually trusted user populations where separation is not yet feasible. There is no setting that restricts the port-proxy without also disabling application proxying.\u003c/p\u003e"
}
],
"value": "Until the patched release is applied, operators of multi-user instances can reduce exposure by separating sensitive workloads onto dedicated hosts or per-user isolated environments rather than sharing a single multi-user node; avoiding co-location of sensitive network services on hosts that also run user sessions; and limiting shared-server access to mutually trusted user populations where separation is not yet feasible. There is no setting that restricts the port-proxy without also disabling application proxying."
}
],
"x_generator": {
"engine": "Vulnogram 0.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "8c484e69-127d-402b-9cdb-5f86ef43eb86",
"assignerShortName": "POSIT",
"cveId": "CVE-2026-121880",
"datePublished": "2026-11-06T15:10:37.306Z",
"dateReserved": "2026-11-04T10:49:21.246Z",
"dateUpdated": "2026-11-06T17:45:27.737Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-121880",
"date": "2026-11-09",
"epss": "0.00252",
"percentile": "0.16827"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"collectionURL": "https://posit.co/download/rstudio-server-pro/",
"cpes": [
"cpe:2.3:a:posit:workbench:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"localhost port-proxy (/p/\u003ctoken\u003e/)"
],
"platforms": [
"Linux"
],
"product": "Posit Workbench",
"programFiles": [
"src/cpp/core/http/UrlPorts.cpp"
],
"vendor": "Posit Software, PBC",
"versions": [
{
"lessThan": "2026.08.0",
"status": "affected",
"version": "0",
"versionType": "custom"
}
]
},
{
"collectionURL": "https://posit.co/download/rstudio-server/",
"cpes": [
"cpe:2.3:a:posit:rstudio_server:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"localhost port-proxy (/p/\u003ctoken\u003e/)"
],
"platforms": [
"Linux"
],
"product": "RStudio Server",
"programFiles": [
"src/cpp/core/http/UrlPorts.cpp"
],
"vendor": "Posit Software, PBC",
"versions": [
{
"lessThan": "2026.08.0",
"status": "affected",
"version": "0",
"versionType": "custom"
}
]
}
],
"source": "8c484e69-127d-402b-9cdb-5f86ef43eb86"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "Authorization bypass through user-controlled key in the localhost port-proxy (/p/\u003ctoken\u003e/) in Posit Software, PBC RStudio Server and Posit Workbench before 2026.08.0 allows remote authenticated users to reach web applications and other services bound to 127.0.0.1 under a different user\u0027s session, and to view their live rendered content and data, via a proxy URL constructed from the attacker\u0027s own port token for an arbitrary port number. The port token is a documented obfuscation measure and not an authorization boundary, and the proxy does not verify that the requested port belongs to the requesting user\u0027s session.\n\n\n\nNOTE: exploitation requires an authenticated account on the same multi-user server and a target service listening on localhost at the time of access. Impact may be greater on hosts that co-locate additional privileged localhost services, and the bypass is not prevented by allow-shell=false; no setting restricts the port-proxy without disabling all application proxying."
}
],
"id": "CVE-2026-121880",
"lastModified": "2026-11-06T20:38:53.570",
"metrics": {
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "YES",
"Recovery": "AUTOMATIC",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 4.7,
"baseSeverity": "MEDIUM",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "PROOF_OF_CONCEPT",
"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": "LOW",
"providerUrgency": "AMBER",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "DIFFUSE",
"vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:P/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:Y/R:A/V:D/RE:M/U:Amber",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "MODERATE"
},
"source": "8c484e69-127d-402b-9cdb-5f86ef43eb86",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-121880",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-11-06T17:21:05.517519Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-11-06T16:17:52.943",
"references": [
{
"source": "8c484e69-127d-402b-9cdb-5f86ef43eb86",
"url": "https://docs.posit.co/ide/news/#rstudio-2026.08.0"
},
{
"source": "8c484e69-127d-402b-9cdb-5f86ef43eb86",
"url": "https://trust.posit.co/updates"
}
],
"sourceIdentifier": "8c484e69-127d-402b-9cdb-5f86ef43eb86",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-639"
},
{
"lang": "en",
"value": "CWE-862"
}
],
"source": "8c484e69-127d-402b-9cdb-5f86ef43eb86",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-121880",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-11-06T17:21:05.517519Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-11-06T17:45:22.097Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://posit.co/download/rstudio-server-pro/",
"cpes": [
"cpe:2.3:a:posit:workbench:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"localhost port-proxy (/p/\u003ctoken\u003e/)"
],
"platforms": [
"Linux"
],
"product": "Posit Workbench",
"programFiles": [
"src/cpp/core/http/UrlPorts.cpp"
],
"vendor": "Posit Software, PBC",
"versions": [
{
"lessThan": "2026.08.0",
"status": "affected",
"version": "0",
"versionType": "custom"
}
]
},
{
"collectionURL": "https://posit.co/download/rstudio-server/",
"cpes": [
"cpe:2.3:a:posit:rstudio_server:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"localhost port-proxy (/p/\u003ctoken\u003e/)"
],
"platforms": [
"Linux"
],
"product": "RStudio Server",
"programFiles": [
"src/cpp/core/http/UrlPorts.cpp"
],
"vendor": "Posit Software, PBC",
"versions": [
{
"lessThan": "2026.08.0",
"status": "affected",
"version": "0",
"versionType": "custom"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAffects multi-user RStudio Server / Posit Workbench deployments in which more than one user has an interactive session on the same host and application proxying via the localhost port-proxy is enabled (the default).\u0026nbsp;\u003c/p\u003e"
}
],
"value": "Affects multi-user RStudio Server / Posit Workbench deployments in which more than one user has an interactive session on the same host and application proxying via the localhost port-proxy is enabled (the default)."
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Luiz Felipe Mol (confu53)"
}
],
"datePublic": "2026-11-04T11:03:00.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAuthorization bypass through user-controlled key in the localhost port-proxy (\u003ccode\u003e/p/\u0026lt;token\u0026gt;/\u003c/code\u003e) in Posit Software, PBC RStudio Server and Posit Workbench before 2026.08.0 allows remote authenticated users to reach web applications and other services bound to 127.0.0.1 under a different user\u0027s session, and to view their live rendered content and data, via a proxy URL constructed from the attacker\u0027s own port token for an arbitrary port number. The port token is a documented obfuscation measure and not an authorization boundary, and the proxy does not verify that the requested port belongs to the requesting user\u0027s session.\u003c/p\u003e\u003cp\u003eNOTE: exploitation requires an authenticated account on the same multi-user server and a target service listening on localhost at the time of access. Impact may be greater on hosts that co-locate additional privileged localhost services, and the bypass is not prevented by \u003ccode\u003eallow-shell=false\u003c/code\u003e; no setting restricts the port-proxy without disabling all application proxying.\u003c/p\u003e"
}
],
"value": "Authorization bypass through user-controlled key in the localhost port-proxy (/p/\u003ctoken\u003e/) in Posit Software, PBC RStudio Server and Posit Workbench before 2026.08.0 allows remote authenticated users to reach web applications and other services bound to 127.0.0.1 under a different user\u0027s session, and to view their live rendered content and data, via a proxy URL constructed from the attacker\u0027s own port token for an arbitrary port number. The port token is a documented obfuscation measure and not an authorization boundary, and the proxy does not verify that the requested port belongs to the requesting user\u0027s session.\n\n\n\nNOTE: exploitation requires an authenticated account on the same multi-user server and a target service listening on localhost at the time of access. Impact may be greater on hosts that co-locate additional privileged localhost services, and the bypass is not prevented by allow-shell=false; no setting restricts the port-proxy without disabling all application proxying."
}
],
"impacts": [
{
"descriptions": [
{
"lang": "en",
"value": "Information disclosure: an authenticated user can view another user\u0027s running application and the data it renders. Where other network services are bound to localhost on the same host, those services may also become reachable through the proxy, and the potential impact in those deployments depends on what is running and how it is configured."
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "YES",
"Recovery": "AUTOMATIC",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"baseScore": 4.7,
"baseSeverity": "MEDIUM",
"exploitMaturity": "PROOF_OF_CONCEPT",
"privilegesRequired": "LOW",
"providerUrgency": "AMBER",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "DIFFUSE",
"vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:P/AU:Y/R:A/V:D/RE:M/U:Amber",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "MODERATE"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-639",
"description": "CWE-639 Authorization Bypass Through User-Controlled Key",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-862",
"description": "CWE-862 Missing Authorization",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-11-06T15:12:38.657Z",
"orgId": "8c484e69-127d-402b-9cdb-5f86ef43eb86",
"shortName": "POSIT"
},
"references": [
{
"name": "RStudio IDE / RStudio Server release notes",
"tags": [
"release-notes",
"vendor-advisory"
],
"url": "https://docs.posit.co/ide/news/#rstudio-2026.08.0"
},
{
"tags": [
"vendor-advisory"
],
"url": "https://trust.posit.co/updates"
}
],
"solutions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eUpgrade to Posit Workbench 2026.08.0 or later, or RStudio Server 2026.08.0 or later. The patched releases verify that a port requested through the localhost port-proxy belongs to the requesting user\u0027s session.\u003c/p\u003e"
}
],
"value": "Upgrade to Posit Workbench 2026.08.0 or later, or RStudio Server 2026.08.0 or later. The patched releases verify that a port requested through the localhost port-proxy belongs to the requesting user\u0027s session."
}
],
"source": {
"discovery": "EXTERNAL"
},
"timeline": [
{
"lang": "en",
"time": "2026-05-22T00:00:00.000Z",
"value": "Reported to Posit through coordinated disclosure"
},
{
"lang": "en",
"time": "2026-05-22T00:00:00.000Z",
"value": "Reproduced internally with a working proof of concept against Posit Workbench 2025.09"
},
{
"lang": "en",
"time": "2026-07-22T00:00:00.000Z",
"value": "CVE submission and security advisory approved by Posit"
}
],
"title": "RStudio Server / Posit Workbench localhost port-proxy does not enforce per-session port ownership",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eUntil the patched release is applied, operators of multi-user instances can reduce exposure by separating sensitive workloads onto dedicated hosts or per-user isolated environments rather than sharing a single multi-user node; avoiding co-location of sensitive network services on hosts that also run user sessions; and limiting shared-server access to mutually trusted user populations where separation is not yet feasible. There is no setting that restricts the port-proxy without also disabling application proxying.\u003c/p\u003e"
}
],
"value": "Until the patched release is applied, operators of multi-user instances can reduce exposure by separating sensitive workloads onto dedicated hosts or per-user isolated environments rather than sharing a single multi-user node; avoiding co-location of sensitive network services on hosts that also run user sessions; and limiting shared-server access to mutually trusted user populations where separation is not yet feasible. There is no setting that restricts the port-proxy without also disabling application proxying."
}
],
"x_generator": {
"engine": "Vulnogram 0.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "8c484e69-127d-402b-9cdb-5f86ef43eb86",
"assignerShortName": "POSIT",
"cveId": "CVE-2026-121880",
"datePublished": "2026-11-06T15:10:37.306Z",
"dateReserved": "2026-11-04T10:49:21.246Z",
"dateUpdated": "2026-11-06T17:45:27.737Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
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.