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
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).
INFO
Published Date :
June 23, 2026, 4:17 a.m.
Last Modified :
July 8, 2026, 2:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-55653
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 53f830b8-0a3f-465b-8143-3b8a9948e749 | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update OpenSSH to the latest version.
- Ensure FIPS mode is configured correctly.
- Monitor SSH server for abnormal behavior.
Public PoC/Exploit Available at Github
CVE-2026-55653 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-55653.
| URL | Resource |
|---|---|
| https://access.redhat.com/errata/RHSA-2026:36759 | |
| https://access.redhat.com/security/cve/CVE-2026-55653 | Vendor Advisory |
| https://bugzilla.redhat.com/show_bug.cgi?id=2462351 | Exploit Issue Tracking Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-55653 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-55653
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
None
Python
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-55653 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-55653 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by [email protected]
Jul. 08, 2026
Action Type Old Value New Value Added Reference https://access.redhat.com/errata/RHSA-2026:36759 Changed Affected [{'cpes': ['cpe:/o:redhat:enterprise_linux:10'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 7', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:hummingbird:1'], 'vendor': 'Red Hat', 'product': 'Red Hat Hardened Images', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'packageName': 'rhcos', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}] [{'cpes': ['cpe:/a:redhat:hummingbird:1'], 'vendor': 'Red Hat', 'product': 'Red Hat Hardened Images', 'versions': [{'status': 'unaffected', 'version': '10.3p1-6.hum1', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'openssh-main', 'collectionURL': 'https://catalog.redhat.com/software/containers/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 7', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'packageName': 'rhcos', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}] -
Initial Analysis by [email protected]
Jun. 25, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:* *cpe:2.3:o:redhat:enterprise_linux:6.0:*:*:*:*:*:*:* *cpe:2.3:a:openbsd:openssh:-:*:*:*:*:*:*:* *cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:* *cpe:2.3:a:redhat:openshift_container_platform:4.0:*:*:*:*:*:*:* *cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:* *cpe:2.3:o:redhat:enterprise_linux:10.0:*:*:*:*:*:*:* *cpe:2.3:a:redhat:hardened_images:-:*:*:*:*:*:*:* Added Reference Type Red Hat, Inc.: https://access.redhat.com/security/cve/CVE-2026-55653 Types: Vendor Advisory Added Reference Type Red Hat, Inc.: https://bugzilla.redhat.com/show_bug.cgi?id=2462351 Types: Exploit, Issue Tracking, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 23, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-55653', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-23T14:30:51.025049Z'} -
New CVE Received by [email protected]
Jun. 23, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:/o:redhat:enterprise_linux:10'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 7', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:hummingbird:1'], 'vendor': 'Red Hat', 'product': 'Red Hat Hardened Images', 'packageName': 'openssh', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'packageName': 'rhcos', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}] Added 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). Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L Added CWE CWE-415 Added Reference https://access.redhat.com/security/cve/CVE-2026-55653 Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2462351