CVE-2026-55653

MEDIUM

4.3

CVSS v3

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).

CWE-415

How to fix

Remediation Available

opensshRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

Fixed in:main@srcRHSA-2026:36759

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

opensshRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:main@srcRHSA-2026:36759

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-askpassRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-askpassRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-askpass-debuginfoRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-askpass-debuginfoRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-cavsRed Hat / RHEL

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-cavsRocky

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-cavs-debuginfoRed Hat / RHEL

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-cavs-debuginfoRocky

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-clientsRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-clientsRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-clients-debuginfoRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-clients-debuginfoRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-debuginfoRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-debuginfoRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-debugsourceRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-debugsourceRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-keycatRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-keycatRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-keycat-debuginfoRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-keycat-debuginfoRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-keysignRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

openssh-keysignRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

openssh-keysign-debuginfoRocky

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

openssh-keysign-debuginfoRed Hat / RHEL

Fixed in:0:9.9p1-25.el10_2RHSA-2026:47757

openssh-ldapRocky

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-ldapRed Hat / RHEL

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-ldap-debuginfoRed Hat / RHEL

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

openssh-ldap-debuginfoRocky

Fixed in:0:8.0p1-30.el8_10RHSA-2026:47755

This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityLow

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

Exploit Intelligence

0.30%probability of exploitation in 30 days

22ndpercentile

Low risk: more likely to be exploited than 22% of all known CVEs.

References

Exploit1

bugzilla.redhat.com

Vendor Advisory1

access.redhat.com

Other references6

Related Vulnerabilities

Other CWE-415 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-25136	Medium	6.5	90%	-	Fix
CVE-2003-0545	Critical	9.8	87%	-	Fix
CVE-2018-0101	Critical	10.0	87%	-	Fix
CVE-2026-33824	Critical	9.8	73%	KEV	Fix
CVE-2019-3829	Medium	5.3	59%	-	Fix
CVE-2021-3407	Medium	5.5	50%	-	Fix

Common questions

How do I fix CVE-2026-55653?

Published advisories record a fix for 50 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Is CVE-2026-55653 being actively exploited?

Not that we know of. CVE-2026-55653 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.30% is the estimated probability that it will be exploited in the next 30 days. That is higher than 22% of all scored CVEs.

How severe is CVE-2026-55653?

CVE-2026-55653 has a CVSS v3 base score of 4.3, rated moderate. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-55653 affect?

Published advisories record a fix for openssh (Rocky), openssh (Red Hat / RHEL), openssh-askpass (Rocky), openssh-askpass (Red Hat / RHEL), and 46 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-25.