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Enterprise LinuxOperating system · Redhat

CVE-2021-3935

HIGH · 8.1 CVSS v3.1 Published 2021-11-22
Fix available
A fix is available. Upgrade to 1.16.1 or later.
See remediation →
90/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
When PgBouncer is configured to use "cert" authentication, a man-in-the-middle attacker can inject arbitrary SQL queries when a connection is first established, despite the use of TLS certificate verification and encryption. This flaw affects PgBouncer versions prior to 1.16.1.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

When PgBouncer is configured to use 'cert' authentication, a man-in-the-middle attacker can inject arbitrary SQL queries during initial connection establishment, despite TLS certificate verification and encryption being enabled. This vulnerability affects PgBouncer versions prior to 1.16.1 and stems from a flaw in how the cert authentication mode handles the connection handshake.

MitigationUpgrade PgBouncer to version 1.16.1 or later to remediate this vulnerability. If immediate upgrading is not feasible, consider temporarily using alternative authentication methods and ensure TLS enforcement is properly validated at both client and server levels.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Enterprise LinuxOperating system
Affected:= 7.0
FedoraOperating system
Affected:= 35
Debian LinuxOperating system
Affected:= 9.0
PgbouncerApplication
Affected:< 1.16.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed PgBouncer version
    Run 'pgbouncer --version' or check your package manager (e.g., 'rpm -q pgbouncer' on RHEL, 'dpkg -l pgbouncer' on Debian)
    Affected if version is less than 1.16.1
  2. Locate PgBouncer configuration file
    Common locations are /etc/pgbouncer/pgbouncer.ini, /etc/pgbouncer.conf, or check for -c config_file parameter in the startup script
    Affected if configuration file exists and is readable
  3. Verify if 'cert' authentication is configured
    In the configuration file, search for 'auth_type' or 'auth_method' setting. Look for value 'cert'
    Affected if auth_type or auth_method is set to 'cert'
  4. Confirm TLS/SSL is enabled
    In the configuration file, check for 'ssl' parameter set to '1' or 'true', and verify 'tls_ssl' or 'server_ssl' settings
    Affected if TLS/SSL is enabled (this is required for the attack to work despite encryption)
  5. Check client connection configuration
    Review [databases] section and any pool_mode settings to confirm client connections use this PgBouncer instance
    Affected if clients connect to this PgBouncer instance with cert authentication

A user is affected if PgBouncer version is below 1.16.1 AND the configuration uses 'cert' authentication mode with TLS enabled.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.16.1 or later
Fixed in 1.16.1
Interim mitigation

Upgrade PgBouncer to version 1.16.1 or later to remediate this vulnerability. If immediate upgrading is not feasible, consider temporarily using alternative authentication methods and ensure TLS enforcement is properly validated at both client and server levels.

Recommended fix High confidence

PgBouncer 1.16.1

  1. Check the current installed version of PgBouncer using 'pgbouncer --version' or your system's package manager
  2. Upgrade PgBouncer to version 1.16.1 or later using your system's package manager (e.g., 'dnf upgrade pgbouncer', 'apt-get install pgbouncer', or 'yum update pgbouncer')
  3. After upgrading, verify the new version is installed: 'pgbouncer --version'
  4. If PgBouncer is running, restart the service to load the new version (e.g., 'systemctl restart pgbouncer' or 'service pgbouncer restart')
  5. Confirm the service is running and accepting connections with the new version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Enterprise Linux Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-3935 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data