VDB-431962 · CVE-2026-121880 · GCVE-0-2026-121880

Posit Software, PBC Posit Workbench/RStudio Server prior 2026.08.0 Localhost Port-Proxy authorization

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4.1	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Posit Software, PBC Posit Workbench and RStudio Server. It has been declared as problematic. This vulnerability affects unknown code of the component Localhost Port-Proxy. Executing a manipulation can lead to authorization. This vulnerability is tracked as CVE-2026-121880. The attack can be launched remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Posit Software, PBC Posit Workbench and RStudio Server. It has been declared as problematic. This vulnerability affects some unknown processing of the component Localhost Port-Proxy. The manipulation with an unknown input leads to a authorization vulnerability. The CWE definition for the vulnerability is CWE-639. The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data. As an impact it is known to affect confidentiality. CVE summarizes:

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.

The advisory is available at docs.posit.co. This vulnerability was named CVE-2026-121880 since 11/04/2026. The exploitation appears to be easy. The attack can be initiated remotely. The technical details are unknown and an exploit is not available.

It is declared as proof-of-concept.

Upgrading to version 2026.08.0 eliminates this vulnerability.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

Posit Software, PBC

Name

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 4.3
VulDB Meta Temp Score: 4.1

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Authorization
CWE: CWE-639 / CWE-285 / CWE-266
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Yes

Availability: 🔒
Status: Proof-of-Concept
Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Posit Workbench/RStudio Server 2026.08.0

Timelineinfo

11/04/2026 CVE reserved
11/06/2026 +2 days Advisory disclosed
11/06/2026 +0 days VulDB entry created
11/06/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: docs.posit.co
Status: Confirmed

CNA: POSIT
CVE: CVE-2026-121880 (🔒)

GCVE (CVE): GCVE-0-2026-121880
GCVE (VulDB): GCVE-100-431962

Entryinfo

Created: 11/06/2026 16:34
Changes: 11/06/2026 16:34 (71)
Complete: 🔍
Cache ID: 216::103