How severe is CVE-2021-3935?

CVE-2021-3935 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-3935 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3935?

CVE-2021-3935 primarily affects Pgbouncer. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-3935?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-3935 published?

CVE-2021-3935 was published on 2021-11-22 and last updated on 2026-06-17.

CVE-2021-3935

CVE-2021-3935 is a high-severity vulnerability in Pgbouncer with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-295.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 5.1
EPSS exploit prediction: 1% (60th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-295
Affected product: Pgbouncer
Published: 2021-11-22
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-3935?: 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.
How severe is CVE-2021-3935?: CVE-2021-3935 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-3935 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3935?: CVE-2021-3935 primarily affects Pgbouncer. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-3935?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-3935 published?: CVE-2021-3935 was published on 2021-11-22 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:a:pgbouncer:pgbouncer:*:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

More vulnerabilities in Pgbouncer

CVE-2026-6665 — High (CVSS 8.1): The SCRAM code in PgBouncer before 1.25.2 did not check the return value of strlcat() correctly when building the…
CVE-2025-2291 — High (CVSS 8.1): Password can be used past expiry in PgBouncer due to auth_query not taking into account Postgres its VALID UNTIL value,…
CVE-2015-6817 — High (CVSS 8.1): PgBouncer 1.6.x before 1.6.1, when configured with auth_user, allows remote attackers to gain login access as auth_user…
CVE-2026-6664 — High (CVSS 7.5): An integer overflow in network packet parsing code in PgBouncer before 1.25.2 bypasses a boundary check and can lead to…
CVE-2025-12819 — High (CVSS 7.5): Untrusted search path in auth_query connection handler in PgBouncer before 1.25.1 allows an unauthenticated attacker to…
CVE-2015-4054 — High (CVSS 7.5): PgBouncer before 1.5.5 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) by…

All CVEs affecting Pgbouncer →

Other CWE-295 (Improper Certificate Validation) vulnerabilities

CVE-2026-4370 — Critical (CVSS 10.0): A vulnerability was identified in Juju from version 3.2.0 until 3.6.19 and from version 4.0 until 4.0.4, where the…
CVE-2026-30836 — Critical (CVSS 10.0): Step CA is an online certificate authority for secure, automated certificate management for DevOps. Versions 0.30.0-rc6…
CVE-2025-68121 — Critical (CVSS 10.0): During session resumption in crypto/tls, if the underlying Config has its ClientCAs or RootCAs fields mutated between…
CVE-2022-20703 — Critical (CVSS 10.0): Multiple vulnerabilities in Cisco Small Business RV160, RV260, RV340, and RV345 Series Routers could allow an attacker…
CVE-2021-1471 — Critical (CVSS 9.9): Multiple vulnerabilities in Cisco Jabber for Windows, Cisco Jabber for MacOS, and Cisco Jabber for mobile platforms…
CVE-2026-20184 — Critical (CVSS 9.8): A vulnerability in the integration of single sign-on (SSO) with Control Hub in Cisco Webex Services could have allowed…

Browse all CWE-295 (Improper Certificate Validation) vulnerabilities →