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CVE-2026-58210

NATS Server: MQTT partial CONNECT packets can exhaust pre-auth memory

7.5 HighFix available

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.74%Unchanged since Jul 9, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.5

NATS Server: MQTT partial CONNECT packets can exhaust pre-auth memory

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Record
CVE-2026-58210
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
EUVDEUVD-2026-42348 7.5

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Record
EUVD-2026-42348
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
NVD 7.5

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Record
CVE-2026-58210
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
OSV 7.5

NATS Server: MQTT partial CONNECT packets can exhaust pre-auth memory

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Record
CVE-2026-58210
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
OSVDEBIAN-CVE-2026-58210 7.5

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Record
DEBIAN-CVE-2026-58210
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
OSVJLSEC-2026-1147 7.5

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Record
JLSEC-2026-1147
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
Show 4 moreShow less
OSVRHSA-2026:36016 7.5

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

Record
RHSA-2026:36016
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
OSVRHSA-2026:36017 7.5

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

Record
RHSA-2026:36017
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-2026-58210 7.5

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Record
UBUNTU-CVE-2026-58210
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
OSVBIT-nats-2026-58210 No score

NATS Server: MQTT partial CONNECT packets can exhaust pre-auth memory

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Record
BIT-nats-2026-58210
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
nats
Bitnami
 before 2.12.12, 2.14.0 up to 2.14.3
2.12.122.14.3
nats-server
Debian:12
 All versions, plus listed versions
2.10.1-12.10.16-12.10.18-12.10.24-12.10.27-1
Show 11 moreShow less
2.10.3-12.10.4-12.10.7-12.12.4-12.12.6-12.14.1-12.14.3-12.14.6-12.15.1-12.9.10-12.9.19-1
 None known
nats-server
Debian:13
 All versions, plus listed versions
2.10.27-12.12.4-12.12.6-12.14.1-12.14.3-12.14.6-12.15.1-1
 None known
nats-server
Debian:14
 before 2.14.3-1, plus listed versions
2.10.27-12.12.4-12.12.6-12.14.1-1
2.14.3-1
nats_server_jll
Julia
 before 2.14.3+0
2.14.3+0
nats-server2.14
Red Hat:hummingbird:1
From an advisory covering 6 CVEs
 before 0:2.14.3-1.hum1
0:2.14.3-1.hum1
nats-server2.12
Red Hat:hummingbird:1
From an advisory covering 6 CVEs
 before 0:2.12.12-1.hum1
0:2.12.12-1.hum1
nats-server
Ubuntu:24.04:LTS
 All versions, plus listed versions
2.9.19-1build12.10.3-12.10.4-12.10.7-12.10.7-1ubuntu0.12.10.7-1ubuntu0.22.10.7-1ubuntu0.3
 None known
nats-server
Ubuntu:25.10
 All versions, plus listed versions
2.10.24-12.10.27-1
 None known
nats-server
Ubuntu:26.10
 All versions, plus listed versions
2.10.27-1build12.14.1-12.14.3-1
 None known
nats-server
Ubuntu:Pro:26.04:LTS
 All versions, plus listed versions
2.10.27-12.10.27-1build12.10.27-1ubuntu0.26.04.1~esm1
 None known

History

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

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

In short

CVE-2026-58210 is a high vulnerability (CVSS 7.5) in Linuxfoundation Nats-server, published July 8, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.74%, the 54th percentile. Fixed in nats 2.12.12.

References

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