chore(deps): update dependency ujson to v5.12.0 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
ujson	5.11.0 → 5.12.0

GitHub Vulnerability Alerts

CVE-2026-32875

Summary

ujson.dumps() crashes the Python interpreter (segmentation fault) when the product of the indent parameter and the nested depth of the input exceeds INT32_MAX. It can also get stuck in an infinite loop if the indent is a large negative number. Both are caused by an integer overflow/underflow whilst calculating how much memory to reserve for indentation. And both can be used to achieve denial of service.

(Note: A negative indent to ujson means add spaces after colons but do not add line breaks or indentation. It is unclear to the current maintainers whether this was ever even an intended feature or just a byproduct of the way it was written.)

Exploitability

To be vulnerable, a service must call ujson.dump()/ujson.dumps()/ujson.encode() whilst giving untrusted users control over the indent parameter and not restrict that indentation to reasonably small non-negative values. (Even with the fix for this vulnerability, such usage is strongly advised against since even a bug-free JSON serialiser would be vulnerable to denial of service simply by the attacker requesting indents that have the server needlessly filling out gigabytes of whitespace.)

A service may also be vulnerable to the infinite loop if it uses a fixed negative indent. An underflow always occurs for any negative indent when the input data is at least one level nested but, for small negative indents, the underflow is usually accidentally rectified by another overflow. As far as the maintainers are aware, the infinite loop can not be reached for indentations from -1 to -65536 / max_recursion_depth_as_limited_by_stack_size but users of negative indents are encouraged to consider their service affected even if the infinite loop seems unreachable.

Example

import ujson

def example(depth, indent):
    a = [0]
    for i in range(1000):
        a = [a]
    ujson.dumps(a, indent=indent)

example(1, 2**30)  # segfault
example(1000, -200)  # infinite loop

Patches

ujson 5.12.0, containing 486bd4553dc471a1de11613bc7347a6b318e37ea, promotes the integer types where the overflow occurred, skips the indentation code path for negative indent (which was supposed to be a no-op) and places an artificial cap of 1000 on the indent parameter.

Workarounds

Users who don't wish to upgrade can either use a fixed indentation, no indentation or ensure indentation is non-negative and not enormous (below 2**31 / max_recursion_depth_as_limited_by_stack_size).

References

The original bug report can be found at https://github.com/ultrajson/ultrajson/issues/700

This issue was independently discovered by @​coco1629, @​EthanKim88 and @​vmfunc.

CVE-2026-32874

Summary

ujson 5.4.0 to 5.11.0 inclusive contain an accumulating memory leak in JSON parsing large (outside of the range [-2^63, 2^64 - 1]) integers.

Exploitability

Any service that calls ujson.load()/ujson.loads()/ujson.decode() on untrusted inputs is affected and vulnerable to denial of service attacks.

Details

The leaked memory is a copy of the string form of the integer plus an additional NULL byte. The leak occurs irrespective of whether the integer parses successfully or is rejected due to having more than sys.get_int_max_str_digits() digits, meaning that any sized leak per malicious JSON can be achieved provided that there is no limit on the overall size of the payload.

ujson.loads(str(2 ** 64 - 1))  # No leak
ujson.loads(str(2 ** 64))  # Leaks
ujson.loads(str(10 ** sys.get_int_max_str_digits()))  # Leaks and raises ValueError

Fix

The leak is fixed in ujson 5.12.0 (4baeb950df780092bd3c89fc702a868e99a3a1d2). There are no workarounds beyond upgrading to an unaffected version.

Credits

Discovered by Cameron Criswell/Skevros using Coverage-guided fuzzing (libFuzzer + AddressSanitizer)

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Release Notes

ultrajson/ultrajson (ujson)

v5.12.0

Compare Source

Added

• Update license field (#​693) @​wagenrace
• Build wheels for GraalPy (#​685) @​timfel

Changed

• Drop support for Python 3.9 (#​686) @​hugovk

Fixed

• Fix buffer overflow/infinite loop from indent handling (#​709) @​bwoodsend
• Remove upper bound of setuptools for PyPy (#​704) @​hugovk

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