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CVE-2021-3935

27
FAUCET Score

CVE-2021-3935 describes a critical man-in-the-middle vulnerability in PgBouncer versions prior to 1.16.1, affecting products like Debian, Fedora, and Red Hat. Despite TLS certificate verification, an attacker can inject arbitrary SQL queries during initial connection establishment when "cert" authentication is used. This vulnerability carries a high CVSS score of 8.1, indicating high impact on confidentiality, integrity, and availability, with a network attack vector and high attack complexity. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.16.1CPE matchmatch criteria
cpe:2.3:a:pgbouncer:pgbouncer:*:*:*:*:*:*:*:*
7.0CPE matchmatch criteria
cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*
35CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.1HIGH

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.03%
Probability of exploitation in next 30 days
EPSS Percentile
60.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0103 is in the 24th percentile among its peer group of 8,918 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

microsoftpatch availablevia msrc
Product: 18853-16820Fixed in: 1.16.1-1
microsoftpatch availablevia msrc
Product: cm1 pgbouncer 1.16.1-1 on CBL Mariner 1.0Fixed in: 1.16.1-1

Vendor Advisories (1)

microsoft2021-Nov/CVE-2021-3935Important

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.

Nov 9, 2021

References

lists.debian.org / debian-lts-announce/2025/05/msg00032.html
bugzilla.redhat.com / show_bug.cgi
Issue TrackingThird Party Advisory
lists.debian.org / debian-lts-announce/2022/02/msg00016.html
Mailing ListThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/TNPCV3KRDI5PLLLKADFVIOHACQJLZMLI
pgbouncer.org / changelog.html
Release NotesVendor Advisory