The uproot library dynamically generates Python class source code from ROOT TStreamerInfo records and compiles it at runtime. Certain file-controlled streamer metadata fields, such as streamer element names, are inserted into the generated Python source without proper quoting via repr() or the !r format specifier. An attacker controlling a ROOT file can insert malicious Python expression-breaking content into these metadata fields. When uproot generates and executes the corresponding reader method, the injected Python code is evaluated in the context of the process opening the file, resulting in arbitrary code execution. This vulnerability affects any application using affected uproot code paths to open or process attacker-controlled ROOT files.

Successful exploitation allows an attacker to execute arbitrary Python code within the context of the application processing the malicious ROOT file. This can lead to full compromise of the application environment, unauthorized actions, data manipulation, or further attacks. The vulnerability requires the attacker to supply a crafted ROOT file and for the victim to open or process it using the vulnerable uproot code.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, avoid processing untrusted ROOT files with affected versions of uproot. Monitor vendor channels for updates and apply patches once released.