CVE-2025-4565
MEDIUM5.3EPSS 0.02%protobuf-python has a potential Denial of Service issue
Description
### Summary Any project that uses Protobuf pure-Python backend to parse untrusted Protocol Buffers data containing an arbitrary number of **recursive groups**, **recursive messages** or **a series of [`SGROUP`](https://protobuf.dev/programming-guides/encoding/#groups) tags** can be corrupted by exceeding the Python recursion limit. Reporter: Alexis Challande, Trail of Bits Ecosystem Security Team [[email protected]](mailto:[email protected]) Affected versions: This issue only affects the [pure-Python implementation](https://github.com/protocolbuffers/protobuf/tree/main/python#implementation-backends) of protobuf-python backend. This is the implementation when `PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python` environment variable is set or the default when protobuf is used from Bazel or pure-Python PyPi wheels. CPython PyPi wheels do not use pure-Python by default. This is a Python variant of a [previous issue affecting protobuf-java](https://github.com/protocolbuffers/protobuf/security/advisories/GHSA-735f-pc8j-v9w8). ### Severity This is a potential Denial of Service. Parsing nested protobuf data creates unbounded recursions that can be abused by an attacker. ### Proof of Concept For reproduction details, please refer to the unit tests [decoder_test.py](https://github.com/protocolbuffers/protobuf/blob/main/python/google/protobuf/internal/decoder_test.py#L87-L98) and [message_test](https://github.com/protocolbuffers/protobuf/blob/main/python/google/protobuf/internal/message_test.py#L1436-L1478) ### Remediation and Mitigation A mitigation is available now. Please update to the latest available versions of the following packages: * protobuf-python(4.25.8, 5.29.5, 6.31.1)
Affected packages (2)
- Debian/protobuffrom 0
- PyPI/protobuffrom 0, < 4.25.8
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
| osv | CVSS 3.1 | MEDIUM5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
References (9)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2025-4565
- ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2025-4565
- PATCHhttps://github.com/protocolbuffers/protobuf
- WEBhttps://github.com/protocolbuffers/protobuf/blob/main/python/google/protobuf/internal/decoder_test.py#L87-L98
- WEBhttps://github.com/protocolbuffers/protobuf/blob/main/python/google/protobuf/internal/message_test.py#L1436-L1478
- WEBhttps://github.com/protocolbuffers/protobuf/commit/17838beda2943d08b8a9d4df5b68f5f04f26d901
- WEBhttps://github.com/protocolbuffers/protobuf/security/advisories/GHSA-735f-pc8j-v9w8
- WEBhttps://github.com/protocolbuffers/protobuf/security/advisories/GHSA-8qvm-5x2c-j2w7
- WEBhttps://github.com/protocolbuffers/protobuf/tree/main/python#implementation-backends