CVE-2025-4565: Any project that uses Protobuf Pure-Python backend to parse untrusted Protocol Buffers data containing an arbi

Routine

MEDIUM 5.3REMOTEUPGRADE

CVE-2025-4565 is a medium-severity flaw (CVSS 5.3) affecting protobuf-python. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 tags can be corrupted by exceeding the Python recursion limit. This can result in a Denial of service by crashing the application with a RecursionError. We recommend upgrading to version =>6.31.1 or beyond commit 17838beda2943d08b8a9d4df5b68f5f04f26d901

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 83%)
CISA exploited list	No
Weakness	CWE-674
Published	2025-06-16
Last modified	2026-06-17

Publisher (CNA): Google Inc. · Vendor: google

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-06-16 15:15 UTCPublished CVE record published
2026-06-17 09:33 UTCUpdated Record last modified

google protobuf-python UPGRADE

Affected: < 4.25.8 · >= 5.26.0 and < 5.29.5 · >= 6.30.0 and < 6.31.1

Fixed in: 4.25.8, 5.29.5, 6.31.1

Safe to downgrade to: a release before 5.26.0

1. Check installed version

apt-cache policy protobuf-python || rpm -q protobuf-python || protobuf-python --version

2. UPGRADE to 4.25.8 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade protobuf-python

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade protobuf-python

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.26.0 (Debian / Ubuntu)

apt-cache madison protobuf-python sudo apt install protobuf-python=<VERSION_BEFORE_5.26.0> sudo apt-mark hold protobuf-python

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list protobuf-python sudo dnf downgrade protobuf-python-<VERSION_BEFORE_5.26.0> sudo dnf versionlock add protobuf-python

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-4565?

protobuf-python: upgrade to 4.25.8, 5.29.5, 6.31.1. Exact commands for each OS are on this page.

Is CVE-2025-4565 being exploited?

CVE-2025-4565 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-4565 affect?

CVE-2025-4565 affects protobuf-python. Severity is medium (CVSS 5.3). 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 tags can be corrupted by exceeding the Python recursion

How urgent is CVE-2025-4565?

Priority 28/100. Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities

References

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