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HIGH severity

Apache Pulsar Disabled Certificate Validation for OAuth Client Credential Requests makes C++/Python Clients vulnerable to MITM attackGHSA-5r3h-c3r7-9w4h

HIGHFix: apache/pulsar#16064

GHSA-5r3h-c3r7-9w4h is a high-severity (CVSS 8.1) CWE-295 vulnerability in pulsar-client. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for pulsar-client — see the affected versions and patch details below.

Also known asCVE-2022-33684PYSEC-2026-901
Published
Updated
Affected
4 pkgs
Patched
4 / 4
Exploits
1 known
Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-5r3h-c3r7-9w4h.

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs61th percentile — riskier than 61% of all scored CVEsHighest risk
0.00%0.48%0.95%1.43%0.1%0.9%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

4 pkgs affected
🐍pulsar-client🐍pulsar-client🐍pulsar-client🐍pulsar-client

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

The Apache Pulsar C++ Client does not verify peer TLS certificates when making HTTPS calls for the OAuth2.0 Client Credential Flow, even when tlsAllowInsecureConnection is disabled via configuration. This vulnerability allows an attacker to perform a man in the middle attack and intercept and/or modify the GET request that is sent to the ClientCredentialFlow "issuer url". The intercepted credentials can be used to acquire authentication data from the OAuth2.0 server to then authenticate with an Apache Pulsar cluster. An attacker can only take advantage of this vulnerability by taking control of a machine "between" the client and the server. The attacker must then actively manipulate traffic to perform the attack. The Apache Pulsar Python Client wraps the C++ client, so it is also vulnerable in the same way.

This issue affects Apache Pulsar C++ Client and Python Client versions 2.7.0 to 2.7.4; 2.8.0 to 2.8.3; 2.9.0 to 2.9.2; 2.10.0 to 2.10.1; 2.6.4 and earlier.

Any users running affected versions of the C++ Client or the Python Client should rotate vulnerable OAuth2.0 credentials, including client_id and client_secret.

  • 2.7 C++ and Python Client users should upgrade to 2.7.5 and rotate vulnerable OAuth2.0 credentials.
  • 2.8 C++ and Python Client users should upgrade to 2.8.4 and rotate vulnerable OAuth2.0 credentials.
  • 2.9 C++ and Python Client users should upgrade to 2.9.3 and rotate vulnerable OAuth2.0 credentials.
  • 2.10 C++ and Python Client users should upgrade to 2.10.2 and rotate vulnerable OAuth2.0 credentials. 3.0 C++ users are unaffected and 3.0 Python Client users will be unaffected when it is released.
  • Any users running the C++ and Python Client for 2.6 or less should upgrade to one of the above patched versions.

Affected Packages

4 total 4 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIpulsar-clientall versions2.7.5pip install --upgrade 'pulsar-client==2.7.5'
🐍PyPIpulsar-client≥ 2.8.0&&< 2.8.42.8.4pip install --upgrade 'pulsar-client==2.8.4'
🐍PyPIpulsar-client≥ 2.9.0&&< 2.9.32.9.3pip install --upgrade 'pulsar-client==2.9.3'
🐍PyPIpulsar-client≥ 2.10.0&&< 2.10.22.10.2pip install --upgrade 'pulsar-client==2.10.2'

Affected Products

1 product · 5 configurations
Application
pulsarapache
≥ 2.10.0 && ≤ 2.6.4
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

The Apache Pulsar C++ Client does not verify peer TLS certificates when …

huntr.devNVDJan 2023

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pulsar-client, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update pulsar-client to 2.7.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5r3h-c3r7-9w4h is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

The Apache Pulsar C++ Client does not verify peer TLS certificates when making HTTPS calls for the OAuth2.0 Client Credential Flow, even when `tlsAllowInsecureConnection` is disabled via configuration. This vulnerability allows an attacker to perform a man in the middle attack and intercept and/or modify the GET request that is sent to the `ClientCredentialFlow` "issuer url". The intercepted credentials can be used to acquire authentication data from the OAuth2.0 server to then authenticate with an Apache Pulsar cluster. An attacker can only take advantage of this vulnerability by taking contr
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