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EPSS 0.3%top 79%

A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-Hellman Group Exchange (DH-GEX) client path.

0
Medium
VulnerabilityCVE-2026-55653gcveosvubuntu-cve-2026-55653ubuntu-pro-14-04-ltsubuntu-pro-16-04-ltsubuntu-pro-fips-16-04-ltsubuntu-pro-18-04-ltsubuntu-18-04-ltsubuntu-pro-fips-updates-18-04-ubuntu-pro-fips-18-04-ltsubuntu-pro-20-04-ltsubuntu-20-04-ltsubuntu-pro-fips-updates-20-04-ubuntu-pro-fips-20-04-ltsubuntu-22-04-ltsubuntu-pro-fips-preview-22-04-ubuntu-pro-fips-updates-22-04-ubuntu-24-04-ltsubuntu-pro-fips-updates-24-04-ubuntu-25-10ubuntu-26-04-lts
Published: 06/23/2026 (06/23/2026, 04:17:00 UTC)
Source: GCVE Database
Product: openssh

Description

A flaw was found in OpenSSH. A malicious SSH server can exploit a double free vulnerability in the Diffie-Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of Service (DoS).

CVSS v3.1

Score 4.3medium

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

Affected software

Ubuntu:Pro:14.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:6.6p1-2ubuntu2.13+esm2?arch=source&distro=esm-infra-legacy/trusty
Affected versions
=1:6.2p2-6=1:6.2p2-6ubuntu1=1:6.4p1-1=1:6.4p1-2=1:6.5p1-1=1:6.5p1-2=1:6.5p1-3=1:6.5p1-4=1:6.5p1-6=1:6.6p1-1=1:6.6p1-2=1:6.6p1-2ubuntu1=1:6.6p1-2ubuntu2=1:6.6p1-2ubuntu2.2=1:6.6p1-2ubuntu2.3=1:6.6p1-2ubuntu2.4=1:6.6p1-2ubuntu2.6=1:6.6p1-2ubuntu2.7=1:6.6p1-2ubuntu2.8=1:6.6p1-2ubuntu2.10=1:6.6p1-2ubuntu2.11=1:6.6p1-2ubuntu2.12=1:6.6p1-2ubuntu2.13=1:6.6p1-2ubuntu2.13+esm1=1:6.6p1-2ubuntu2.13+esm2
Ubuntu:Pro:16.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.2p2-4ubuntu2.10+esm9?arch=source&distro=esm-infra-legacy/xenial
Affected versions
=1:6.9p1-2=1:6.9p1-3=1:7.1p1-1=1:7.1p1-3=1:7.1p1-4=1:7.1p1-6=1:7.1p2-1=1:7.1p2-2=1:7.2p1-1=1:7.2p2-1=1:7.2p2-2=1:7.2p2-3=1:7.2p2-4=1:7.2p2-4ubuntu1=1:7.2p2-4ubuntu2.1=1:7.2p2-4ubuntu2.2=1:7.2p2-4ubuntu2.4=1:7.2p2-4ubuntu2.5=1:7.2p2-4ubuntu2.6=1:7.2p2-4ubuntu2.7=1:7.2p2-4ubuntu2.8=1:7.2p2-4ubuntu2.10=1:7.2p2-4ubuntu2.10+esm1=1:7.2p2-4ubuntu2.10+esm2=1:7.2p2-4ubuntu2.10+esm3=1:7.2p2-4ubuntu2.10+esm4=1:7.2p2-4ubuntu2.10+esm5=1:7.2p2-4ubuntu2.10+esm6=1:7.2p2-4ubuntu2.10+esm7=1:7.2p2-4ubuntu2.10+esm8=1:7.2p2-4ubuntu2.10+esm9
Ubuntu:Pro:FIPS:16.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.2p2-4ubuntu2.fips.2.10.7?arch=source&distro=fips-updates/xenial
Affected versions
=1:7.2p2-4ubuntu2.fips.2.2.3=1:7.2p2-4ubuntu2.fips.2.4.1=1:7.2p2-4ubuntu2.fips.2.4.2=1:7.2p2-4ubuntu2.fips.2.8.1=1:7.2p2-4ubuntu2.fips.2.10.1=1:7.2p2-4ubuntu2.fips.2.10.2=1:7.2p2-4ubuntu2.fips.2.10.3=1:7.2p2-4ubuntu2.fips.2.10.4=1:7.2p2-4ubuntu2.fips.2.10.5=1:7.2p2-4ubuntu2.fips.2.10.6=1:7.2p2-4ubuntu2.fips.2.10.7
Ubuntu:Pro:FIPS:16.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.2p2-4ubuntu2.fips.2.10.1?arch=source&distro=fips/xenial
Affected versions
=1:7.2p2-4ubuntu2.fips.2.2=1:7.2p2-4ubuntu2.fips.2.2.1=1:7.2p2-4ubuntu2.fips.2.10.1
Ubuntu:Pro:18.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.6p1-4ubuntu0.7+esm4?arch=source&distro=esm-infra/bionic
Affected versions
=1:7.5p1-10=1:7.6p1-4=1:7.6p1-4ubuntu0.1=1:7.6p1-4ubuntu0.2=1:7.6p1-4ubuntu0.3=1:7.6p1-4ubuntu0.5=1:7.6p1-4ubuntu0.6=1:7.6p1-4ubuntu0.7=1:7.6p1-4ubuntu0.7+esm1=1:7.6p1-4ubuntu0.7+esm2=1:7.6p1-4ubuntu0.7+esm3=1:7.6p1-4ubuntu0.7+esm4
Ubuntu:18.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1@1:7.5p1-10?arch=source&distro=bionic
Affected versions
=1:7.5p1-8=1:7.5p1-9=1:7.5p1-9build1=1:7.5p1-10
Ubuntu:Pro:FIPS-updates:18.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.9p1-10~ubuntu18.04.fips.0.10?arch=source&distro=fips-updates/bionic
Affected versions
=1:7.9p1-10~ubuntu18.04.fips.0.1=1:7.9p1-10~ubuntu18.04.fips.0.2=1:7.9p1-10~ubuntu18.04.fips.0.3=1:7.9p1-10~ubuntu18.04.fips.0.4=1:7.9p1-10~ubuntu18.04.fips.0.5=1:7.9p1-10~ubuntu18.04.fips.0.6=1:7.9p1-10~ubuntu18.04.fips.0.7=1:7.9p1-10~ubuntu18.04.fips.0.8=1:7.9p1-10~ubuntu18.04.fips.0.9=1:7.9p1-10~ubuntu18.04.fips.0.10
Ubuntu:Pro:FIPS:18.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.9p1-10~ubuntu18.04.fips.0.2?arch=source&distro=fips/bionic
Affected versions
=1:7.9p1-10~ubuntu18.04.fips.0.1=1:7.9p1-10~ubuntu18.04.fips.0.2
Ubuntu:Pro:20.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.2p1-4ubuntu0.13+esm1?arch=source&distro=esm-infra/focal
Affected versions
=1:8.0p1-6build1=1:8.1p1-1=1:8.1p1-5=1:8.2p1-4=1:8.2p1-4ubuntu0.1=1:8.2p1-4ubuntu0.2=1:8.2p1-4ubuntu0.3=1:8.2p1-4ubuntu0.4=1:8.2p1-4ubuntu0.5=1:8.2p1-4ubuntu0.7=1:8.2p1-4ubuntu0.8=1:8.2p1-4ubuntu0.9=1:8.2p1-4ubuntu0.10=1:8.2p1-4ubuntu0.11=1:8.2p1-4ubuntu0.12=1:8.2p1-4ubuntu0.13=1:8.2p1-4ubuntu0.13+esm1
Ubuntu:20.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1@1:7.5p1-11build1?arch=source&distro=focal
Affected versions
=1:7.5p1-11build1
Ubuntu:Pro:FIPS-updates:20.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.2p1-4ubuntu0.fips.0.13.1?arch=source&distro=fips-updates/focal
Affected versions
=1:8.2p1-4ubuntu0.fips.0.2.1=1:8.2p1-4ubuntu0.fips.0.4.0=1:8.2p1-4ubuntu0.fips.0.5.0=1:8.2p1-4ubuntu0.fips.0.7=1:8.2p1-4ubuntu0.fips.0.8=1:8.2p1-4ubuntu0.fips.0.9=1:8.2p1-4ubuntu0.fips.0.10=1:8.2p1-4ubuntu0.fips.0.11=1:8.2p1-4ubuntu0.fips.0.12=1:8.2p1-4ubuntu0.fips.0.13=1:8.2p1-4ubuntu0.fips.0.13.1
Ubuntu:Pro:FIPS:20.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.2p1-4ubuntu0.fips.0.2.1?arch=source&distro=fips/focal
Affected versions
=1:8.2p1-4ubuntu0.fips.0.2.1
Ubuntu:22.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1@1:7.5p1-13?arch=source&distro=jammy
Affected versions
=1:7.5p1-12=1:7.5p1-12build1=1:7.5p1-13
Ubuntu:Pro:FIPS-preview:22.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.9p1-3ubuntu1.fips.0~ppa3?arch=source&distro=fips-preview/jammy
Affected versions
=1:8.9p1-3ubuntu0.4+Fips1=1:8.9p1-3ubuntu0.4+Fips3=1:8.9p1-3ubuntu1.fips.0~ppa3
Ubuntu:Pro:FIPS-updates:22.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.9p1-3ubuntu1.fips.0~ppa3?arch=source&distro=fips-updates/jammy
Affected versions
=1:8.9p1-3ubuntu0.4+Fips1=1:8.9p1-3ubuntu0.4+Fips3=1:8.9p1-3ubuntu0.6+Fips1=1:8.9p1-3ubuntu0.7+Fips1=1:8.9p1-3ubuntu0.10+Fips1=1:8.9p1-3ubuntu0.11+Fips1=1:8.9p1-3ubuntu0.13+Fips1=1:8.9p1-3ubuntu0.14+Fips1=1:8.9p1-3ubuntu0.15+Fips1=1:8.9p1-3ubuntu0.15+Fips3=1:8.9p1-3ubuntu0.16+Fips3=1:8.9p1-3ubuntu1.fips.0~ppa3
Ubuntu:24.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1@1:7.5p1-16?arch=source&distro=noble
Affected versions
=1:7.5p1-14=1:7.5p1-15=1:7.5p1-15build1=1:7.5p1-16
Ubuntu:Pro:FIPS-updates:24.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:9.6p1-3ubuntu13.18+Fips1?arch=source&distro=fips-updates/noble
Affected versions
=1:9.6p1-3ubuntu13.7+Fips1=1:9.6p1-3ubuntu13.12+Fips1=1:9.6p1-3ubuntu13.13+Fips1=1:9.6p1-3ubuntu13.14+Fips1=1:9.6p1-3ubuntu13.15+Fips1=1:9.6p1-3ubuntu13.16+Fips1=1:9.6p1-3ubuntu13.16+Fips2=1:9.6p1-3ubuntu13.18+Fips1
Ubuntu:25.10more threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1@1:7.5p1-17?arch=source&distro=questing
Affected versions
=1:7.5p1-17
Ubuntu:26.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1@1:7.5p1-18?arch=source&distro=resolute
Affected versions
=1:7.5p1-17=1:7.5p1-18

Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.

Technical Details

Gcve Source
db.gcve.eu
Osv Id
UBUNTU-CVE-2026-55653
Osv Schema Version
1.7.0
Aliases
[]
Ecosystems
["Ubuntu:Pro:14.04:LTS","Ubuntu:Pro:16.04:LTS","Ubuntu:Pro:FIPS:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:18.04:LTS","Ubuntu:Pro:FIPS-updates:18.04:LTS","Ubuntu:Pro:FIPS:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:20.04:LTS","Ubuntu:Pro:FIPS-updates:20.04:LTS","Ubuntu:Pro:FIPS:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:Pro:FIPS-preview:22.04:LTS","Ubuntu:Pro:FIPS-updates:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:Pro:FIPS-updates:24.04:LTS","Ubuntu:25.10","Ubuntu:26.04:LTS"]
Database Specific Severity
null
Cvss Version
3.1

Threat ID: 6a5fd06a1010f89cc218b48c

Added to database: 07/21/2026, 20:02:50 UTC

Last updated: 07/31/2026, 19:24:46 UTC

Views: 7

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