CVE-2026-0994: Protobuf Protobuf Affected By A JSON Vulnerability

HIGH
Advisory Identifier: GHSA-7gcm-g887-7qv7
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CWE-674
Published
Advisory Summary

CVE-2026-0994 is a HIGH protobuf affected by a json vulnerability (CWE-674: Uncontrolled Recursion) affecting Protobuf libraries in the PyPI ecosystem. The issue involves protobuf affected by a json recursion depth bypass. Remediation is available by upgrading affected packages to version 6.33.5, 5.29.6.

CVE-2026-0994 at a Glance

CVE Identifier CVE-2026-0994
GHSA Identifier GHSA-7gcm-g887-7qv7
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-674: Uncontrolled Recursion
Affected Product Protobuf
Package Ecosystem PyPI
Published Date
Last Updated

How to Fix CVE-2026-0994

To remediate this vulnerability, upgrade all affected Protobuf dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

protobuf fixed: 6.33.5 
pip install protobuf>=6.33.5
protobuf fixed: 5.29.6 
pip install protobuf>=5.29.6
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show protobuf

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-0994, inspect your installed packages using pip:

pip show protobuf

Analyze the terminal output to locate any version of Protobuf in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.33.5), your application is affected.

Note: The pip show protobuf command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-674: Uncontrolled Recursion, where the product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack. In Protobuf, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A denial-of-service (DoS) vulnerability exists in google.protobuf.json_format.ParseDict() in Python, where the max_recursion_depth limit can be bypassed when parsing nested google.protobuf.Any messages. Due to missing recursion depth accounting inside the internal Any-handling logic, an attacker can supply deeply nested Any structures that bypass the intended recursion limit, eventually exhausting Python’s recursion stack and causing a RecursionError.

CVE-2026-0994 Affected Protobuf Versions

2 component(s)
Fixed Versions:
6.33.55.29.6
Product / Package Ecosystem Affected Versions Fixed Version
protobuf
pypi/protobuf
PyPI
≥ 6.30.0rc1
< 6.33.5
6.33.5
protobuf
pypi/protobuf
PyPI
< 5.29.6
5.29.6

References

NVD — CVE-2026-0994 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-0994
Protobuf Source Repository REPOSITORY
https://github.com/protocolbuffers/protobuf/issues/25070
Protobuf Source Repository REPOSITORY
https://github.com/protocolbuffers/protobuf/pull/25239
Security Fix Commit FIX COMMIT
https://github.com/protocolbuffers/protobuf/commit/5ebddcb1bcbe51d1fe323baa145e85f4f23128cf
Security Fix Commit FIX COMMIT
https://github.com/protocolbuffers/protobuf/commit/d2b001626d137c62dfee6c88c87324102531868b
Protobuf Source Repository REPOSITORY
https://github.com/protocolbuffers/protobuf

Frequently Asked Questions

What is CVE-2026-0994?
CVE-2026-0994 is a security vulnerability in Protobuf involving protobuf affected by a JSON recursion depth bypass under CWE-674: Uncontrolled Recursion.
Which Protobuf versions are affected?
Affected versions include releases prior to 6.33.5, 5.29.6 across affected packages: protobuf.
What version fixes CVE-2026-0994?
Upgrading to 6.33.5, 5.29.6 (or the latest patched release for your respective branch) resolves the vulnerability.
Is protobuf affected?
Yes, protobuf is affected in releases prior to 6.33.5, 5.29.6. Upgrade your dependency to 6.33.5, 5.29.6 or later.
What CWE is associated with CVE-2026-0994?
CVE-2026-0994 is classified under 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.).
How can I check PyPI dependencies for CVE-2026-0994?
Run the dependency tree command: 'pip show protobuf'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7gcm-g887-7qv7",
  "modified" : "2026-02-05T15:47:43Z",
  "published" : "2026-01-23T15:31:35Z",
  "aliases" : [ "CVE-2026-0994" ],
  "summary" : "protobuf affected by a JSON recursion depth bypass",
  "details" : "A denial-of-service (DoS) vulnerability exists in google.protobuf.json_format.ParseDict() in Python, where the max_recursion_depth limit can be bypassed when parsing nested google.protobuf.Any messages.\n\nDue to missing recursion depth accounting inside the internal Any-handling logic, an attacker can supply deeply nested Any structures that bypass the intended recursion limit, eventually exhausting Python’s recursion stack and causing a RecursionError.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "protobuf"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "6.30.0rc1"
      }, {
        "fixed" : "6.33.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.33.4"
    }
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "protobuf"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.29.6"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-0994"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/protocolbuffers/protobuf/issues/25070"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/protocolbuffers/protobuf/pull/25239"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/protocolbuffers/protobuf/commit/5ebddcb1bcbe51d1fe323baa145e85f4f23128cf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/protocolbuffers/protobuf/commit/d2b001626d137c62dfee6c88c87324102531868b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/protocolbuffers/protobuf"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-674" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-01-23T16:56:33Z",
    "nvd_published_at" : "2026-01-23T15:16:06Z"
  }
}