OpenSSH Diffie-Hellman Group Exchange double free

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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4.2$25k-$100k10.00

Summaryinfo

A vulnerability classified as problematic has been found in OpenSSH. This issue affects some unknown processing of the component Diffie-Hellman Group Exchange. This manipulation causes double free. This vulnerability is registered as CVE-2026-55653. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in OpenSSH (version now known). It has been declared as problematic. Affected by this vulnerability is some unknown processing of the component Diffie-Hellman Group Exchange. The manipulation with an unknown input leads to a double free vulnerability. The CWE definition for the vulnerability is CWE-415. The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations. As an impact it is known to affect availability. The summary by CVE is:

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).

The advisory is shared at access.redhat.com. This vulnerability is known as CVE-2026-55653 since 06/17/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $25k-$100k at the moment (estimation calculated on 06/23/2026).

The vulnerability scanner Nessus provides a plugin with the ID 322159 (Linux Distros Unpatched Vulnerability : CVE-2026-55653), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the databases at Tenable (322159), EUVD (EUVD-2026-38412) and CERT Bund (WID-SEC-2026-2039). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

  • Open Source OpenSSH

Productinfo

Type

Name

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.3
VulDB Meta Temp Score: 4.2

VulDB Base Score: 4.3
VulDB Temp Score: 4.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 4.3
CNA Vector (redhat): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Double free
CWE: CWE-415 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 322159
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-55653

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

06/17/2026 CVE reserved
06/23/2026 +6 days Advisory disclosed
06/23/2026 +0 days VulDB entry created
06/23/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: access.redhat.com
Status: Not defined

CVE: CVE-2026-55653 (🔒)
GCVE (CVE): GCVE-0-2026-55653
GCVE (VulDB): GCVE-100-372805
EUVD: 🔒
CERT Bund: WID-SEC-2026-2039 - OpenSSH: Mehrere Schwachstellen

Entryinfo

Created: 06/23/2026 07:03
Updated: 06/23/2026 16:57
Changes: 06/23/2026 07:03 (60), 06/23/2026 08:33 (1), 06/23/2026 15:51 (7), 06/23/2026 16:57 (2)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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