# 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

CVE-2026-55653 is fixed in 17 products on 1 platform, first by ALSA-2026:47757, released July 29, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-55653
- Priority: High
- CVSS: 7.7 (Moderate)
- EPSS: 0.0053
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 22, 2026
- Weakness: Double Free
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55653

## Description

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.  Security Fix(es):  * openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Red Hat Enterprise Linux OpenSSH client versions (CVE-2026-55655)  * 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 (CVE-2026-55653)  For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | openssh RHEL 10 | 9.9p1-7.el10_0.5 | [RHSA-2026:76748](https://patchblox.com/security/data/fix/linux/rhsa-2026-76748.md) | Jul 31, 2026 |
| Linux | openssh RHEL 8 | 0:8.0p1-30.el8_10 | [RHSA-2026:47755](https://patchblox.com/security/data/fix/linux/rhsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh RHEL 9 | 0:9.9p1-9.el9_8 | [RHSA-2026:47756](https://patchblox.com/security/data/fix/linux/rhsa-2026-47756.md) | Jul 31, 2026 |
| Linux | openssh almalinux 10 | 9.9p1-25.el10_2.alma.1 | [ALSA-2026:47757](https://patchblox.com/security/data/fix/linux/alsa-2026-47757.md) | Jul 29, 2026 |
| Linux | openssh almalinux 8 | 8.0p1-30.el8_10 | [ALSA-2026:47755](https://patchblox.com/security/data/fix/linux/alsa-2026-47755.md) | Jul 29, 2026 |
| Linux | openssh almalinux 9 | 9.9p1-9.el9_8.alma.1 | [ALSA-2026:47756](https://patchblox.com/security/data/fix/linux/alsa-2026-47756.md) | Jul 29, 2026 |
| Linux | openssh amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh ol 10 | 0:9.9p1-25.0.1.el10_2 | [ELSA-2026-47757](https://patchblox.com/security/data/fix/linux/elsa-2026-47757.md) | Jul 30, 2026 |
| Linux | openssh ol 8 | 0:8.0p1-30.0.1.el8_10 | [ELSA-2026-47755](https://patchblox.com/security/data/fix/linux/elsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh ol 9 | 0:9.9p1-9.0.1.el9_8 | [ELSA-2026-47756](https://patchblox.com/security/data/fix/linux/elsa-2026-47756.md) | Aug 6, 2026 |
| Linux | openssh rocky 10 | 0:9.9p1-25.el10_2.rocky.0.1 | [RLSA-2026:47757](https://patchblox.com/security/data/fix/linux/rlsa-2026-47757.md) | Jul 30, 2026 |
| Linux | openssh rocky 8 | 0:8.0p1-30.el8_10 | [RLSA-2026:47755](https://patchblox.com/security/data/fix/linux/rlsa-2026-47755.md) | Jul 30, 2026 |
| Linux | openssh rocky 9 | 0:9.9p1-9.el9_8.rocky.0.1 | [RLSA-2026:47756](https://patchblox.com/security/data/fix/linux/rlsa-2026-47756.md) | Jul 30, 2026 |
| Linux | openssh-askpass RHEL 8 | 0:8.0p1-30.el8_10 | [RHSA-2026:47755](https://patchblox.com/security/data/fix/linux/rhsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-askpass RHEL 9 | 0:9.9p1-9.el9_8 | [RHSA-2026:47756](https://patchblox.com/security/data/fix/linux/rhsa-2026-47756.md) | Jul 31, 2026 |
| Linux | openssh-askpass almalinux 10 | 9.9p1-25.el10_2.alma.1 | [ALSA-2026:47757](https://patchblox.com/security/data/fix/linux/alsa-2026-47757.md) | Jul 29, 2026 |
| Linux | openssh-askpass almalinux 8 | 8.0p1-30.el8_10 | [ALSA-2026:47755](https://patchblox.com/security/data/fix/linux/alsa-2026-47755.md) | Jul 29, 2026 |
| Linux | openssh-askpass almalinux 9 | 9.9p1-9.el9_8.alma.1 | [ALSA-2026:47756](https://patchblox.com/security/data/fix/linux/alsa-2026-47756.md) | Jul 29, 2026 |
| Linux | openssh-askpass ol 10 | 0:9.9p1-25.0.1.el10_2 | [ELSA-2026-47757](https://patchblox.com/security/data/fix/linux/elsa-2026-47757.md) | Jul 30, 2026 |
| Linux | openssh-askpass ol 8 | 0:8.0p1-30.0.1.el8_10 | [ELSA-2026-47755](https://patchblox.com/security/data/fix/linux/elsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-askpass ol 9 | 0:9.9p1-9.0.1.el9_8 | [ELSA-2026-47756](https://patchblox.com/security/data/fix/linux/elsa-2026-47756.md) | Aug 6, 2026 |
| Linux | openssh-cavs RHEL 8 | 0:8.0p1-30.el8_10 | [RHSA-2026:47755](https://patchblox.com/security/data/fix/linux/rhsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-cavs almalinux 8 | 8.0p1-30.el8_10 | [ALSA-2026:47755](https://patchblox.com/security/data/fix/linux/alsa-2026-47755.md) | Jul 29, 2026 |
| Linux | openssh-cavs ol 8 | 0:8.0p1-30.0.1.el8_10 | [ELSA-2026-47755](https://patchblox.com/security/data/fix/linux/elsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-clients RHEL 8 | 0:8.0p1-30.el8_10 | [RHSA-2026:47755](https://patchblox.com/security/data/fix/linux/rhsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-clients RHEL 9 | 0:9.9p1-9.el9_8 | [RHSA-2026:47756](https://patchblox.com/security/data/fix/linux/rhsa-2026-47756.md) | Jul 31, 2026 |
| Linux | openssh-clients almalinux 10 | 9.9p1-25.el10_2.alma.1 | [ALSA-2026:47757](https://patchblox.com/security/data/fix/linux/alsa-2026-47757.md) | Jul 29, 2026 |
| Linux | openssh-clients almalinux 8 | 8.0p1-30.el8_10 | [ALSA-2026:47755](https://patchblox.com/security/data/fix/linux/alsa-2026-47755.md) | Jul 29, 2026 |
| Linux | openssh-clients almalinux 9 | 9.9p1-9.el9_8.alma.1 | [ALSA-2026:47756](https://patchblox.com/security/data/fix/linux/alsa-2026-47756.md) | Jul 29, 2026 |
| Linux | openssh-clients amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh-clients ol 10 | 0:9.9p1-25.0.1.el10_2 | [ELSA-2026-47757](https://patchblox.com/security/data/fix/linux/elsa-2026-47757.md) | Jul 30, 2026 |
| Linux | openssh-clients ol 8 | 0:8.0p1-30.0.1.el8_10 | [ELSA-2026-47755](https://patchblox.com/security/data/fix/linux/elsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-clients ol 9 | 0:9.9p1-9.0.1.el9_8 | [ELSA-2026-47756](https://patchblox.com/security/data/fix/linux/elsa-2026-47756.md) | Aug 6, 2026 |
| Linux | openssh-clients-debuginfo amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh-debuginfo amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh-debugsource amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh-keycat RHEL 8 | 0:8.0p1-30.el8_10 | [RHSA-2026:47755](https://patchblox.com/security/data/fix/linux/rhsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-keycat RHEL 9 | 0:9.9p1-9.el9_8 | [RHSA-2026:47756](https://patchblox.com/security/data/fix/linux/rhsa-2026-47756.md) | Jul 31, 2026 |
| Linux | openssh-keycat almalinux 10 | 9.9p1-25.el10_2.alma.1 | [ALSA-2026:47757](https://patchblox.com/security/data/fix/linux/alsa-2026-47757.md) | Jul 29, 2026 |
| Linux | openssh-keycat almalinux 8 | 8.0p1-30.el8_10 | [ALSA-2026:47755](https://patchblox.com/security/data/fix/linux/alsa-2026-47755.md) | Jul 29, 2026 |
| Linux | openssh-keycat almalinux 9 | 9.9p1-9.el9_8.alma.1 | [ALSA-2026:47756](https://patchblox.com/security/data/fix/linux/alsa-2026-47756.md) | Jul 29, 2026 |
| Linux | openssh-keycat amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh-keycat ol 10 | 0:9.9p1-25.0.1.el10_2 | [ELSA-2026-47757](https://patchblox.com/security/data/fix/linux/elsa-2026-47757.md) | Jul 30, 2026 |
| Linux | openssh-keycat ol 8 | 0:8.0p1-30.0.1.el8_10 | [ELSA-2026-47755](https://patchblox.com/security/data/fix/linux/elsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-keycat ol 9 | 0:9.9p1-9.0.1.el9_8 | [ELSA-2026-47756](https://patchblox.com/security/data/fix/linux/elsa-2026-47756.md) | Aug 6, 2026 |
| Linux | openssh-keycat-debuginfo amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh-keysign almalinux 10 | 9.9p1-25.el10_2.alma.1 | [ALSA-2026:47757](https://patchblox.com/security/data/fix/linux/alsa-2026-47757.md) | Jul 29, 2026 |
| Linux | openssh-keysign ol 10 | 0:9.9p1-25.0.1.el10_2 | [ELSA-2026-47757](https://patchblox.com/security/data/fix/linux/elsa-2026-47757.md) | Jul 30, 2026 |
| Linux | openssh-ldap RHEL 8 | 0:8.0p1-30.el8_10 | [RHSA-2026:47755](https://patchblox.com/security/data/fix/linux/rhsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-ldap almalinux 8 | 8.0p1-30.el8_10 | [ALSA-2026:47755](https://patchblox.com/security/data/fix/linux/alsa-2026-47755.md) | Jul 29, 2026 |
| Linux | openssh-ldap ol 8 | 0:8.0p1-30.0.1.el8_10 | [ELSA-2026-47755](https://patchblox.com/security/data/fix/linux/elsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-server RHEL 8 | 0:8.0p1-30.el8_10 | [RHSA-2026:47755](https://patchblox.com/security/data/fix/linux/rhsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-server RHEL 9 | 0:9.9p1-9.el9_8 | [RHSA-2026:47756](https://patchblox.com/security/data/fix/linux/rhsa-2026-47756.md) | Jul 31, 2026 |
| Linux | openssh-server almalinux 10 | 9.9p1-25.el10_2.alma.1 | [ALSA-2026:47757](https://patchblox.com/security/data/fix/linux/alsa-2026-47757.md) | Jul 29, 2026 |
| Linux | openssh-server almalinux 8 | 8.0p1-30.el8_10 | [ALSA-2026:47755](https://patchblox.com/security/data/fix/linux/alsa-2026-47755.md) | Jul 29, 2026 |
| Linux | openssh-server almalinux 9 | 9.9p1-9.el9_8.alma.1 | [ALSA-2026:47756](https://patchblox.com/security/data/fix/linux/alsa-2026-47756.md) | Jul 29, 2026 |
| Linux | openssh-server amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh-server ol 10 | 0:9.9p1-25.0.1.el10_2 | [ELSA-2026-47757](https://patchblox.com/security/data/fix/linux/elsa-2026-47757.md) | Jul 30, 2026 |
| Linux | openssh-server ol 8 | 0:8.0p1-30.0.1.el8_10 | [ELSA-2026-47755](https://patchblox.com/security/data/fix/linux/elsa-2026-47755.md) | Jul 31, 2026 |
| Linux | openssh-server ol 9 | 0:9.9p1-9.0.1.el9_8 | [ELSA-2026-47756](https://patchblox.com/security/data/fix/linux/elsa-2026-47756.md) | Aug 6, 2026 |
| Linux | openssh-server-debuginfo amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh-sk-dummy amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | openssh-sk-dummy-debuginfo amzn 2023 | 9.9p1-10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | pam_ssh_agent_auth RHEL 8 | 0:0.10.3-7.30.el8_10 | [RHSA-2026:47755](https://patchblox.com/security/data/fix/linux/rhsa-2026-47755.md) | Jul 31, 2026 |
| Linux | pam_ssh_agent_auth RHEL 9 | 0:0.10.4-7.9.el9_8 | [RHSA-2026:47756](https://patchblox.com/security/data/fix/linux/rhsa-2026-47756.md) | Jul 31, 2026 |
| Linux | pam_ssh_agent_auth almalinux 8 | 0.10.3-7.30.el8_10 | [ALSA-2026:47755](https://patchblox.com/security/data/fix/linux/alsa-2026-47755.md) | Jul 29, 2026 |
| Linux | pam_ssh_agent_auth almalinux 9 | 0.10.4-7.9.el9_8.alma.1 | [ALSA-2026:47756](https://patchblox.com/security/data/fix/linux/alsa-2026-47756.md) | Jul 29, 2026 |
| Linux | pam_ssh_agent_auth amzn 2023 | 0.10.4-9.10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |
| Linux | pam_ssh_agent_auth ol 8 | 0:0.10.3-7.30.0.1.el8_10 | [ELSA-2026-47755](https://patchblox.com/security/data/fix/linux/elsa-2026-47755.md) | Jul 31, 2026 |
| Linux | pam_ssh_agent_auth ol 9 | 0:0.10.4-7.9.0.1.el9_8 | [ELSA-2026-47756](https://patchblox.com/security/data/fix/linux/elsa-2026-47756.md) | Aug 6, 2026 |
| Linux | pam_ssh_agent_auth-debuginfo amzn 2023 | 0.10.4-9.10.amzn2023.0.1 | [ALAS2023-2026-2031](https://patchblox.com/security/data/fix/linux/alas2023-2026-2031.md) | Aug 3, 2026 |

---

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