RStudio Server / Posit Workbench localhost port-proxy does not enforce per-session port ownership
CVSS score
4.7
EPSS probability
—
Risk score
0.5
Published
1 d ago
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Vulnerability description
DayBreach AI Explanation
Verified against sourcesSources read
1
Source agreement
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Evidence confidence
%55
Short explanation
An authorization bypass vulnerability exists in the localhost port-proxy mechanism of RStudio Server and Posit Workbench. This flaw allows authenticated users to access data belonging to other sessions.
The vulnerability creates privacy risks on multi-user servers by allowing authenticated users to view the contents and data of different user sessions.
What should be done?
- Monitor official vendor advisories and security updates
- Apply the recommended patches according to vendor guidance
Chain of evidence and sources
RStudio Server ve Posit Workbench 2026.08.0 öncesi sürümlerde yetkilendirme atlatma açığı bulunmaktadır.
Açığın istismarı, aynı çok kullanıcılı sunucuda kimliği doğrulanmış bir hesap ve hedef servisin dinlemede olmasını gerektirir.
Show the technical text from the sources
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.
CVSS vector: 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
CWE: CWE-639, CWE-862
This explanation was compiled automatically from the source records. Scores, active exploitation, patch and exploit status come straight from the sources.
IMPACT: Affected Products and Software
RED HAT CSAF/VEX: Product Impact Check
SCORING: CVSS from Multiple Sources
CVSS Scores
The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.
| SCORE | VERSION | SEVERITY | VECTOR | SOURCE |
|---|---|---|---|---|
| 4.7 | CVSS V4_0 | MEDIUM | 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 | CVE CNA |
| 4.7 | CVSS V40 | MEDIUM | 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 | NVD |
Patch and Remediation Guide
Solution & Remediation Advisory
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Public exploit and active exploitation status
Verified exploit intelligence
No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.
Weakness Classification and Attack Patterns (CWE & CAPEC)
CWE - Common Weakness Enumeration
While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-121880 is associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-121880 weaknesses.
Attack Vector and Accessibility
Official Sources and Advisories
CVSS Vector Radar Chart
4.7 / 10Vulnerability Scoring Details
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:AmberYama durumu bilinmiyor
Weakness Type (CWE & CAPEC)
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