Is there a public exploit for CVE-2026-121880?

No public exploit for CVE-2026-121880 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-121880?

CVE-2026-121880 scores CVSS 4.7 (v4.0), rated medium.

What does CVE-2026-121880 affect?

CVE-2026-121880 affects Posit Software, PBC Posit Workbench, RStudio Server.

4.7 Medium

Authorization bypass through user-controlled key in the localhost port-proxy (/p/ /) in Posit Software, PBC RStudio Server and Posit…

CVE-2026-121880

Authorization bypass through user-controlled key in the localhost port-proxy (/p/ /) 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.

Assessment

CVSS: 4.7 (v4.0)
Severity: Medium
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 6 November 2026
Last updated: 6 November 2026
Affected: Posit Software, PBC · Posit Workbench · RStudio Server
Assigner: POSIT

CVSS vectorCVSS: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

At the source

EUVD (ENISA)

References

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