CVE-2026-58203: NestedSecretsSettingsSource follows symlinks outside secrets_dir, enabling local file read and bypassing secrets_dir_max_size

pydantic-settings provides settings management using Pydantic. From 2.12.0 until 2.14.2, NestedSecretsSettingsSource reads secret values from files in a configured secretsdir. When secretsnestedsubdir=True, a directory entry inside secretsdir that is a symbolic link pointing outside secretsdir is followed, so files outside the configured directory are read into settings values. The same code path bypasses the documented secretsdirmaxsize protection. An attacker or lower-privileged component able to influence entries in the configured secrets directory (for example, a writable or shared secrets mount) can turn this into an unintended local file read into settings and can defeat the advertised loading-size cap. This vulnerability is fixed in 2.14.2.