Threat Intelligence Database

A memory leak vulnerability exists in the UltraJSON (ujson) library versions 5.4.0 through 5.11.0 when parsing large integers outside the range [-2^63, 2^64 - 1]. This flaw can be triggered by any service using ujson to parse untrusted JSON inputs, potentially leading to denial of service (DoS). The leak involves accumulating copies of the string representation of large integers plus a null byte, regardless of whether parsing succeeds or fails. The issue is fixed in ujson version 5.12.0. No workarounds other than upgrading are available.

CVE-2026-32875 is a vulnerability in the UltraJSON (ujson) library used by python-lsp-server where integer overflow or underflow in handling the 'indent' parameter during JSON serialization can cause a segmentation fault (crash) or an infinite loop. This occurs when the product of the indent value and the nested depth exceeds the 32-bit integer limit or when a large negative indent is used. The issue can lead to denial of service. The vulnerability affects python-lsp-server versions >=1.6.0 and <1.14.0_1. A patch is available in ujson 5.12.0 that fixes the overflow and caps the indent value.

Black is the uncompromising Python code formatter. Black provides a GitHub action for formatting code. This action supports an option, use_pyproject: true, for reading the version of Black to use from the repository pyproject.toml. A malicious pull request could edit pyproject.toml to use a direct URL reference to a malicious repository. This could lead to arbitrary code execution in the context of the GitHub Action. Attackers could then gain access to secrets or permissions available in the context of the action. Version 26.3.0 fixes this vulnerability.

Pallets Click, versions 8.3.2 and below, contain a command injection vulnerability in the click.edit() function, allowing attackers to pass arbitrary OS commands from an unprivileged account.

### Summary When `ujson.dump()` writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. Code that uses `ujson.dumps()` rather than `ujson.dump()` or only JSON load/decode methods is unaffected. ### Details **Vulnerability Location:** - `src/ujson/python/objToJSON.c:913` - `objToJSONFile()` function start - `src/ujson/python/objToJSON.c:931` - Error return on write failure - `src/ujson/python/objToJSON.c:942` - Early return without cleanup **Root Cause:** The `objToJSONFile()` function allocates a Python string object via `ujson_dumps_internal()`, calls the file's `write()` method, and returns early if `write()` raises an exception—but never calls `Py_DECREF(string)` on the early exit path. ### PoC ```python import gc, tracemalloc, ujson class BadFile: def write(self, s): raise RuntimeError("boom") obj = {"x": "A" * 200000} def run(): try: ujson.dump(obj, BadFile()) except RuntimeError: pass run() tracemalloc.start() gc.collect() base = tracemalloc.get_traced_memory()[0] for i in range(5): run() gc.collect() cur = tracemalloc.get_traced_memory()[0] print(i, cur - base) ``` ### Impact Any application that serializes data through `ujson.dump()` to an attacker-influenced file-like object that can fail can be driven into linear memory growth. An attacker can quickly use up all the memory of say a web server that sends JSON responses using `ujson.dump()` by repeatedly making requests then closing the connection mid response. ### Remediation The missing dec-refs were added in 82af1d0ac01d09aa40c887b460d44b9d9f4bccd9. We recommend upgrading to [UltraJSON 5.12.1](https://github.com/ultrajson/ultrajson/releases/tag/5.12.1). ### Workarounds Replacing `ujson.dump(obj, file)` with `file.write(ujson.dumps(obj))` is equivalent (contrary to popular misconception, there are no streaming benefits to using `ujson.dump()`) and will avoid the memory leak.

UltraJSON's ujson.dumps() function with reject_bytes=False may accept malformed or truncated UTF-8 byte sequences and silently rewrite them into different Unicode characters instead of rejecting them. This behavior causes input validation bypass and data integrity issues. The issue affects versions before 5.13.0 and certain python-lsp-server versions. A fix is available in UltraJSON 5.13.0.