CVE-2025-4565
protobuf-python has a potential Denial of Service issue
Impact
### 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 [ecosystem@trailofbits.com](mailto:ecosystem@trailofbits.com) 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
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | protobuf | < 4.25.8 | 4.25.8 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Protobuf-Python | before 4.25.8 from 5.26.0 before 5.29.5 from 6.30.0 before 6.31.1 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/protocolbuffers/protobuf/commit/17838beda2943d08b8a9d4df5b68f5f04f26d901
- https://github.com/advisories/GHSA-8qvm-5x2c-j2w7
- https://github.com/protocolbuffers/protobuf/security/advisories/GHSA-735f-pc8j-v9w8
- https://github.com/protocolbuffers/protobuf/security/advisories/GHSA-8qvm-5x2c-j2w7
- https://nvd.nist.gov/vuln/detail/CVE-2025-4565
- https://github.com/protocolbuffers/protobuf/blob/main/python/google/protobuf/internal/decoder_test.py#L87-L98
- https://github.com/protocolbuffers/protobuf/blob/main/python/google/protobuf/internal/message_test.py#L1436-L1478
- https://github.com/protocolbuffers/protobuf/tree/main/python#implementation-backends