Advisory [CVE-2026-86147] External control of file name or path and uncontrolled resource consumption in Apache bRPC (version < 1.18.0) on all platforms allows remote attackers who can reach the builtin service port to create directories and truncate/overwrite files with the privileges of the server process, or to hold the process-wide CPU/contention profiler for an arbitrarily long time

External control of file name or path and uncontrolled resource consumption in Apache bRPC (version < 1.18.0) on all platforms allows remote attackers who can reach the builtin service port to create directories and truncate/overwrite files with the privileges of the server process, or to hold the process-wide CPU/contention profiler for an arbitrarily long time.

Root Cause: 1.

The builtin /flags service allows gflags carrying a validator to be modified at runtime via?setvalue=. The bvar/mbvar dump path gflags (bvar_dump_file, bvar_dump_tabs, mbvar_dump_file) were registered with an accept-anything validator whose only purpose was to wake the dumping thread.

A remote attacker could therefore repoint the dump path (e.g.

GET /flags/bvar_dump_file?setvalue=/victim/dir/target followed by GET /flags/bvar_dump?setvalue=true, or the equivalent for mbvar_dump_file, which is used verbatim without a forced suffix), making the dumping thread recursively create directories and open/truncate files at attacker-chosen locations.

Tab names in bvar_dump_tabs were appended to the path without sanitization, allowing '..' to escape the configured directory. 2.

The /pprof builtin service did not clamp the?seconds= parameter to FLAGS_max_profiling_seconds (a limit that /hotspots enforced).