CVE-2026-28505: Tautulli: RCE via eval() sandbox bypass using lambda nested scope to escape co_names whitelist check

Severity: critical (CVSS 10.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-03-30 · updated 2026-06-17
Weakness: CWE-94

Description

Tautulli is a Python based monitoring and tracking tool for Plex Media Server. Prior to version 2.17.0, the str_eval() function in notification_handler.py implements a sandboxed eval() for notification text templates. The sandbox attempts to restrict callable names by inspecting code.co_names of the compiled code object. However, co_names only contains names from the outer code object. When a lambda expression is used, it creates a nested code object whose attribute accesses are stored in code.co_consts, NOT in code.co_names. The sandbox never inspects nested code objects. This issue has been patched in version 2.17.0.

Affected products

Tautulli: before 2.17.0 — fixed in 2.17.0

How to fix

Upgrade to a fixed version: Tautulli 2.17.0. Check the vendor advisory for mitigations.

References

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