Medium severity · published Jun 23, 2026
CVE-2026-55653
Openssh: double free in red hat enterprise linux versions of openssh dh-gex client path during fips known-group validation leads to client-side denial of service
6.5
CVSS
0.5%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 45% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 10.0 Extended Update Support · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 6 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 7 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 9 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 9.6 Extended Update Support · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Hardened Images · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat OpenShift AI 3.0 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat OpenShift AI 3.2 · Red Hat
All versions, or not specified · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-55653
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-55653
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:36759
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:47755
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:47756
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:47757
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:54387
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:58981
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