Threats affecting pkg:brew/posting

A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream. Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.

Scrapy versions from 2.7.1 up to but not including 2.10.0 are vulnerable to a denial of service (DoS) attack due to a flaw in the brotli decompression implementation. The existing protection against decompression bombs does not mitigate the brotli variant, allowing crafted compressed data to cause excessive memory consumption and crash clients with less than 80GB of available memory. This vulnerability is fixed in Scrapy version 2.10.0.

### Summary `NestedSecretsSettingsSource` reads secret values from files in a configured `secrets_dir`. When `secrets_nested_subdir=True`, a directory entry inside `secrets_dir` that is a symbolic link pointing **outside** `secrets_dir` is followed, so files outside the configured directory are read into settings values. The same code path bypasses the documented `secrets_dir_max_size` 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 report does not claim network reachability by itself. ### Details `NestedSecretsSettingsSource` performed two passes over `secrets_dir` using two different, inconsistent directory-traversal implementations: * The size check in `validate_secrets_path()` used `Path.glob('**/*')`, which does **not** descend into a symbolically-linked directory. * The loader in `load_secrets()` used `glob.iglob(f'{path}/**/*', recursive=True)` followed by `read_text()`, which **does** follow symlinked directories and reads through the link target. Because the two passes disagreed on symlinks, a symlinked directory inside `secrets_dir` whose target lives elsewhere was invisible to the size accounting (counted as 0 bytes) while still being fully read by the loader. This produces two distinct problems: 1. **Out-of-tree read (CWE-22 / CWE-59).** A symlinked directory (or file) inside `secrets_dir` that resolves outside it is followed, and the external file's contents are loaded into the corresponding settings field. 2. **`secrets_dir_max_size` bypass (CWE-400).** The size check never sees the out-of-tree content, so the documented size cap is neither respected nor able to reject the oversized external file. A related amplification exists for cyclic in-tree symlinks, which `glob.iglob(recursive=True)` re-traverses, inflating the size accounting and the number of loaded secrets. #### Reproduction In a clean Linux container, with a `secrets_dir` containing a symlink `secrets/db -> /path/outside` and an `outside/passwd` file of 512 bytes, while `secrets_dir_max_size=100`: ```python from pydantic import BaseModel from pydantic_settings import ( BaseSettings, SettingsConfigDict, NestedSecretsSettingsSource, ) class Db(BaseModel): passwd: str | None = None class Settings(BaseSettings): model_config = SettingsConfigDict( secrets_dir='secrets', secrets_nested_subdir=True, secrets_dir_max_size=100, # outside/passwd is 512 bytes ) db: Db = Db() @classmethod def settings_customise_sources( cls, settings_cls, init_settings, env_settings, dotenv_settings, file_secret_settings ): return (NestedSecretsSettingsSource(file_secret_settings),) ``` On affected versions, `Settings().db.passwd` is populated with the 512-byte out-of-tree file and **no** `SettingsError` is raised, even though the file exceeds `secrets_dir_max_size`. ### Impact Applications that opt into `NestedSecretsSettingsSource` with `secrets_nested_subdir=True` and load secrets from a directory whose entries can be influenced by an attacker or a lower-privileged component (for example, a writable or shared secrets mount, or a secrets directory partially populated from untrusted input) are affected. The impact is: * **Confidentiality:** files outside the configured `secrets_dir` can be read into settings values (local file read). * **Integrity / availability of the safeguard:** the advertised `secrets_dir_max_size` cap can be bypassed, and cyclic symlinks can inflate resource usage during loading. The vulnerability requires the ability to place a symbolic link inside the configured secrets directory; it is not remotely reachable on its own. Applications that do not use `NestedSecretsSettingsSource`, or that point `secrets_dir` at a directory fully under the application's control, are not affected. ### Mitigation Upgrade to **pydantic-settings 2.14.2**, which: * walks the secrets directory explicitly and only descends into directories whose resolved path stays within `secrets_dir`, so symlinked directories pointing outside are never followed; * uses a single, cycle-safe iterator for both the size check and the loader, so the size accounting and the loaded set are always consistent and each real directory is visited at most once; * skips any file whose resolved path escapes `secrets_dir`, as defense in depth. If upgrading is not immediately possible, ensure the configured `secrets_dir` is fully owned and controlled by the application (no writable or attacker-influenced entries), or avoid `secrets_nested_subdir=True`.

### Impact A leniency in h11's parsing of line terminators in chunked-coding message bodies can lead to request smuggling vulnerabilities under certain conditions. ### Details HTTP/1.1 Chunked-Encoding bodies are formatted as a sequence of "chunks", each of which consists of: - chunk length - `\r\n` - `length` bytes of content - `\r\n` In versions of h11 up to 0.14.0, h11 instead parsed them as: - chunk length - `\r\n` - `length` bytes of content - any two bytes i.e. it did not validate that the trailing `\r\n` bytes were correct, and if you put 2 bytes of garbage there it would be accepted, instead of correctly rejecting the body as malformed. By itself this is harmless. However, suppose you have a proxy or reverse-proxy that tries to analyze HTTP requests, and your proxy has a _different_ bug in parsing Chunked-Encoding, acting as if the format is: - chunk length - `\r\n` - `length` bytes of content - more bytes of content, as many as it takes until you find a `\r\n` For example, [pound](https://github.com/graygnuorg/pound/pull/43) had this bug -- it can happen if an implementer uses a generic "read until end of line" helper to consumes the trailing `\r\n`. In this case, h11 and your proxy may both accept the same stream of bytes, but interpret them differently. For example, consider the following HTTP request(s) (assume all line breaks are `\r\n`): ``` GET /one HTTP/1.1 Host: localhost Transfer-Encoding: chunked 5 AAAAAXX2 45 0 GET /two HTTP/1.1 Host: localhost Transfer-Encoding: chunked 0 ``` Here h11 will interpret it as two requests, one with body `AAAAA45` and one with an empty body, while our hypothetical buggy proxy will interpret it as a single request, with body `AAAAXX20\r\n\r\nGET /two ...`. And any time two HTTP processors both accept the same string of bytes but interpret them differently, you have the conditions for a "request smuggling" attack. For example, if `/two` is a dangerous endpoint and the job of the reverse proxy is to stop requests from getting there, then an attacker could use a bytestream like the above to circumvent this protection. Even worse, if our buggy reverse proxy receives two requests from different users: ``` GET /one HTTP/1.1 Host: localhost Transfer-Encoding: chunked 5 AAAAAXX999 0 ``` ``` GET /two HTTP/1.1 Host: localhost Cookie: SESSION_KEY=abcdef... ``` ...it will consider the first request to be complete and valid, and send both on to the h11-based web server over the same socket. The server will then see the two concatenated requests, and interpret them as _one_ request to `/one` whose body includes `/two`'s session key, potentially allowing one user to steal another's credentials. ### Patches Fixed in h11 0.15.0. ### Workarounds Since exploitation requires the combination of buggy h11 with a buggy (reverse) proxy, fixing either component is sufficient to mitigate this issue. ### Credits Reported by Jeppe Bonde Weikop on 2025-01-09.