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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

CVSS 4.3 · Medium EPSS 0.20% · P10

Possible ATT&CK Techniques 1AI

T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2026-55653

Vulnerability Information
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Vulnerability Title
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
Source: NVD (National Vulnerability Database)
Vulnerability 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).
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
Source: NVD (National Vulnerability Database)
Vulnerability Type
双重释放
Source: NVD (National Vulnerability Database)
Vulnerability Title
OpenSSH 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
OpenSSH OpenSSH是OpenSSH组织的一个安全管理连接的软件。 OpenSSH存在资源管理错误漏洞，该漏洞源于Diffie-Hellman Group Exchange客户端路径存在双重释放漏洞，在FIPS模式已知组验证期间处理攻击者控制的DH-GEX组参数时发生，成功利用会导致客户端进程终止，造成拒绝服务。以下版本受到影响：Red Hat Enterprise Linux 10、Red Hat Enterprise Linux 6、Red Hat Enterprise Linux 7、Re
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
Red HatRed Hat Enterprise Linux 10-cpe:/o:redhat:enterprise_linux:10
Red HatRed Hat Enterprise Linux 6-cpe:/o:redhat:enterprise_linux:6
Red HatRed Hat Enterprise Linux 7-cpe:/o:redhat:enterprise_linux:7
Red HatRed Hat Enterprise Linux 8-cpe:/o:redhat:enterprise_linux:8
Red HatRed Hat Enterprise Linux 9-cpe:/o:redhat:enterprise_linux:9
Red HatRed Hat Hardened Images-cpe:/a:redhat:hummingbird:1
Red HatRed Hat OpenShift Container Platform 4-cpe:/a:redhat:openshift:4

II. Public POCs for CVE-2026-55653

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III. Intelligence Information for CVE-2026-55653

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Vendor Advisories for CVE-2026-55653 (1)

Other References for CVE-2026-55653 (1)

Same Patch Batch · Red Hat · 2026-06-23 · 12 CVEs total

CVE-2026-118079.6 CRITICALEda-server: websocket missing authorization allows credential theft via activation_id spoo
CVE-2026-121127.8 HIGHForeman-mcp-server: mcp server: active session hijacking via insecure session state reuse
CVE-2026-106096.8 MEDIUMOpenshift/cluster-logging-operator: cluster logging operator creates and forwards servicea
CVE-2026-118206.5 MEDIUMCommunity.general: community.general nexmo — api credentials exposed in get url query stri
CVE-2026-90736.2 MEDIUMForeman-mcp-server: mcp server: insecure sensitive http header sanitization
CVE-2026-118195.5 MEDIUMCommunity.general: community.general keyring_info — os keyring passphrase returned in plai
CVE-2026-129695.3 MEDIUMDnsmasq: dnsmasq: out-of-bounds read in find_soa() due to missing extrabytes validation
CVE-2026-556555.0 MEDIUMOpenssh: local mitm of x11 forwarding via abstract unix socket pre-binding in red hat ente
CVE-2026-128924.4 MEDIUMGstreamer1-plugins-bad: gstreamer1-plugins-bad: 1-byte heap out-of-bounds read in h.264 na
CVE-2026-128914.3 MEDIUMGstreamer1-plugins-bad: gstreamer1-plugins-bad: global buffer overflow (oob read) in h.266
CVE-2026-556543.7 LOWOpenssh: heap out-of-bounds read in red hat enterprise linux versions of openssh gssapi in

IV. Related Vulnerabilities

Same product: Red Hat Enterprise Linux 10
Same vendor: Red Hat
Same weakness: CWE-415

V. Comments for CVE-2026-55653

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