Affected: Homebrew: aider

### Summary `PdfParser`'s `get_value()` can recurse without any limit and crash with an uncaught `RecursionError`. It is reachable through `Image.save(im, fp=<pdf>, format="PDF", append=True)` when the existing PDF file is attacker-controlled. This is the same class of bug as https://github.com/advisories/GHSA-r73j-pqj5-w3x7 (the /Prev trailer chain loop, fixed earlier this year), in the same file, but in two different functions that fix did not touch.

### Details **`get_value()` in `src/PIL/PdfParser.py`**

This is a classmethod that takes `max_nesting: int = -1` and has a guard:

```python if max_nesting == 0: return None, None ```

Every recursive call (nested arrays, dictionaries, indirect object definitions) passes `max_nesting=max_nesting - 1`. Since the default and every call site start at -1, this only ever counts down further negative: -1, -2, -3, and so on. It never equals exactly 0, so the guard never runs. A PDF object with a value nested a few thousand levels deep is enough to hit Python's recursion limit. It does not even need a valid `/Pages` tree, since `read_pdf_info()` parses the `/Root` object's own dictionary first, before checking anything else.

This advisory reports a single vulnerability: an ineffective recursion-depth guard in `PdfParser.get_value()` (the sentinel `-1` default never reaches the `== 0` check). The mention of GHSA-r73j-pqj5-w3x7 is comparative context for an already-fixed, already-CVE'd bug in a different function — it is not a…

Affected: python-pillow Pillow

Pillow is a Python imaging library. From 5.1.0 until 13.0.0, Pillow's PdfParser.get_value() can recurse without a limit while reading nested PDF objects. The parser follows attacker-controlled arrays and dictionaries when an existing PDF is opened for append. An attacker can provide a deeply nested PDF to an application that saves an image with PDF append enabled. This can raise an uncaught RecursionError or terminate the worker, causing denial of service. This issue is fixed in version 13.0.0.