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CVE-2026-6669

Unbounded SCRAM iteration count causes CPU exhaustion in PgBouncer

5.9 MediumFix available

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server in PgBouncer through 1.25.2 allows a malicious or compromised PostgreSQL backend to cause uncontrolled CPU consumption in PgBouncer. The resulting key derivation cannot be interrupted in frontend builds such as PgBouncer. Because PgBouncer serves all clients from a single process, one backend can in this way stop it from serving traffic for every other database and client it is pooling, so the failure of a single backend is not contained.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.42%Up 0.1 points since Sep 24, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.9

Unbounded SCRAM iteration count causes CPU exhaustion in PgBouncer

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server in PgBouncer through 1.25.2 allows a malicious or compromised PostgreSQL backend to cause uncontrolled CPU consumption in PgBouncer. The resulting key derivation cannot be interrupted in frontend builds such as PgBouncer. Because PgBouncer serves all clients from a single process, one backend can in this way stop it from serving traffic for every other database and client it is pooling, so the failure of a single backend is not contained.

Record
CVE-2026-6669
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
EUVDEUVD-2026-85364 5.9

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server in PgBouncer through 1.25.2 allows a malicious or compromised PostgreSQL backend to cause uncontrolled CPU consumption in PgBouncer. The resulting key derivation cannot be interrupted in frontend builds such as PgBouncer. Because PgBouncer serves all clients from a single process, one backend can in this way stop it from serving traffic for every other database and client it is pooling, so the failure of a single backend is not contained.

Record
EUVD-2026-85364
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-58j7-v2vx-r29w 5.9

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to...

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server in PgBouncer through 1.25.2 allows a malicious or compromised PostgreSQL backend to cause uncontrolled CPU consumption in PgBouncer. The resulting key derivation cannot be interrupted in frontend builds such as PgBouncer. Because PgBouncer serves all clients from a single process, one backend can in this way stop it from serving traffic for every other database and client it is pooling, so the failure of a single backend is not contained.

Record
GHSA-58j7-v2vx-r29w
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
NVD 5.9

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server in PgBouncer through 1.25.2 allows a malicious or compromised PostgreSQL backend to cause uncontrolled CPU consumption in PgBouncer. The resulting key derivation cannot be interrupted in frontend builds such as PgBouncer. Because PgBouncer serves all clients from a single process, one backend can in this way stop it from serving traffic for every other database and client it is pooling, so the failure of a single backend is not contained.

Record
CVE-2026-6669
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
OSVDEBIAN-CVE-2026-6669 5.9

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server in PgBouncer through 1.25.2 allows a malicious or compromised PostgreSQL backend to cause uncontrolled CPU consumption in PgBouncer. The resulting key derivation cannot be interrupted in frontend builds such as PgBouncer. Because PgBouncer serves all clients from a single process, one backend can in this way stop it from serving traffic for every other database and client it is pooling, so the failure of a single backend is not contained.

Record
DEBIAN-CVE-2026-6669
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVRHSA-2026:70698 7.5

Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

Record
RHSA-2026:70698
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-6669 5.9

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server in PgBouncer through 1.25.2 allows a malicious or compromised PostgreSQL backend to cause uncontrolled CPU consumption in PgBouncer. The resulting key derivation cannot be interrupted in frontend builds such as PgBouncer. Because PgBouncer serves all clients from a single process, one backend can in this way stop it from serving traffic for every other database and client it is pooling, so the failure of a single backend is not contained.

Record
UBUNTU-CVE-2026-6669
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVAZL-105063 No score

CVE-2026-6669 affecting package pgbouncer 1.25.2-1

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server in PgBouncer through 1.25.2 allows a malicious or compromised PostgreSQL backend to cause uncontrolled CPU consumption in PgBouncer. The resulting key derivation cannot be interrupted in frontend builds such as PgBouncer. Because PgBouncer serves all clients from a single process, one backend can in this way stop it from serving traffic for every other database and client it is pooling, so the failure of a single backend is not contained.

Record
AZL-105063
Updated
2026-11-02
OSVBIT-pgbouncer-2026-6669 No score

Unbounded SCRAM iteration count causes CPU exhaustion in PgBouncer

Missing upper bound on the key derivation iteration count accepted during SCRAM authentication to a backend server in PgBouncer through 1.25.2 allows a malicious or compromised PostgreSQL backend to cause uncontrolled CPU consumption in PgBouncer. The resulting key derivation cannot be interrupted in frontend builds such as PgBouncer. Because PgBouncer serves all clients from a single process, one backend can in this way stop it from serving traffic for every other database and client it is pooling, so the failure of a single backend is not contained.

Record
BIT-pgbouncer-2026-6669
Updated
2026-11-02

Affected packages

Affected packages
PackageAffectedFixed
pgbouncer
Azure Linux:3
through 1.25.2-1 None known
pgbouncer
Bitnami
before 1.26.0
1.26.0
pgbouncer
Debian:12
All versions, plus listed versions
1.18.0-11.18.0-1+deb12u11.19.0-11.19.1-11.20.0-1
Show 19 moreShow less
1.20.1-11.21.0-11.22.0-11.22.1-11.23.0-11.23.1-11.24.0-21.24.0-31.24.1-11.25.0-11.25.0-21.25.1-11.25.2-11.26.0-11.26.0-21.26.0-31.26.0-41.26.0-51.26.0-6
None known
pgbouncer
Debian:13
All versions, plus listed versions
1.24.1-11.24.1-1+deb13u11.24.1-1+deb13u21.25.0-11.25.0-2
Show 8 moreShow less
1.25.1-11.25.2-11.26.0-11.26.0-21.26.0-31.26.0-41.26.0-51.26.0-6
None known
pgbouncer
Debian:14
before 1.26.0-1, plus listed versions
1.24.1-11.25.0-11.25.0-21.25.1-11.25.2-1
1.26.0-1
pgbouncer
Red Hat:hummingbird:1
From an advisory covering 3 CVEs
before 0:1.26.0-0.1.hum1
0:1.26.0-0.1.hum1
pgbouncer
Ubuntu:16.04:LTS
All versions, plus listed versions
1.5.5-11.6.1-11.7-1
None known
pgbouncer
Ubuntu:18.04:LTS
All versions, plus listed versions
1.7.2-3build11.7.2-65-g2b8e6cf-11.8.1-11.8.1-1build1
None known
pgbouncer
Ubuntu:20.04:LTS
All versions, plus listed versions
1.10.0-11.10.0-1build11.11.0-11.12.0-21.12.0-3
None known
pgbouncer
Ubuntu:22.04:LTS
All versions, plus listed versions
1.15.0-11.16.1-1ubuntu1
None known
pgbouncer
Ubuntu:24.04:LTS
All versions, plus listed versions
1.20.0-11.21.0-11.22.0-11.22.0-1build11.22.0-1build31.22.0-1build4
None known
pgbouncer
Ubuntu:26.10
All versions, plus listed versions
1.25.1-11.25.2-11.25.2-1ubuntu1
None known
pgbouncer
Ubuntu:26.04:LTS
All versions, plus listed versions
1.24.1-11.25.0-21.25.1-1
None known

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-6669 is a medium vulnerability (CVSS 5.9) in pgbouncer, published September 23, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.42%, the 36th percentile. Fixed in pgbouncer 1.26.0.

References

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