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🛡️ CVE-2025-4565 — protobuf

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-674 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

protobuf-python has a potential Denial of Service issue

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)

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability low.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: Low — limited, and the attacker does not choose what is affected.

Weakness class

CVE-2025-4565 is classified as CWE-674: Uncontrolled Recursion. The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.

Affected software

CVE-2025-4565 is recorded against 2 packages.

  • protobuf (from 6.30.0rc1 up to 6.31.1)
  • protobuf-python (from 6.30.0 up to 6.31.1)

Timeline and source

Published on 7 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Web)
github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
github.com (Package)
github.com (Web)
github.com (Web)
github.com (Web)
pypi.org (Package)
github.com (Advisory)

Other advisories for this package

protobuf has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-674: Uncontrolled Recursion) in other software:

CVE-2025-4565 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CWE CWE-674
Public Exploit ✅ No
Source NVD
Published 2026-07-07
Updated 2026-08-20
Modified 2026-07-07

Affected Packages

Software From version Fixed in
protobuf 6.30.0rc1 6.31.1
protobuf-python 6.30.0 6.31.1

References

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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