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 servic
Noroxi assessment
Priority: Monitor (action score 26/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.53% (FIRST EPSS).
- Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
- Fixed version: azl3 openssh 9.8p1-10 on Azure Linux 3.0 Release Notes.
- Severity is disputed: the assigning authority (CNA) scores it 4.3, NVD 6.5.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to azl3 openssh 9.8p1-10 on Azure Linux 3.0 Release Notes or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
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).
- Published
- Jun 23, 2026
- Updated
- Oct 29, 2026
- EPSS
- 0.5% · 44th percentile
- CWE
- CWE-415
Report tools
Action score
26
Monitor
Low priority for now.
- CVSS
- 26 / 40 · 6.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.5%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 6.5
- CNA · redhat
- 4.3
- 2.2 point gap
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| openbsd | openssh | cpe:2.3:a:openbsd:openssh |
| redhat | hardened images | cpe:2.3:a:redhat:hardened_images |
| redhat | openshift container platform | cpe:2.3:a:redhat:openshift_container_platform |
| redhat | enterprise linux | cpe:2.3:o:redhat:enterprise_linux |
Is OpenSSH on your server exposed to the internet?
The free port scanner finds the open ports on your server and matches the service versions it can read against known vulnerabilities. No account needed.
Run a port scanAffected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- openbsd opensshall versions
- redhat enterprise linux10.0
- redhat enterprise linux6.0
- redhat enterprise linux7.0
- redhat enterprise linux8.0
- redhat enterprise linux9.0
- redhat hardened imagesall versions
- redhat openshift container platform4.0
Versions reported by the vendor
Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.
Red Hat Red Hat Enterprise Linux 10
- 0:9.9p1-25.el10_2 and laternot affected · rpm
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support
- 0:9.9p1-7.el10_0.5 and laternot affected · rpm
Red Hat Red Hat Enterprise Linux 6
- all versionsaffected
Red Hat Red Hat Enterprise Linux 7
- all versionsaffected
Red Hat Red Hat Enterprise Linux 8
- 0:8.0p1-30.el8_10 and laternot affected · rpm
- 0:8.0p1-30.el8_10 and laternot affected · rpm
Red Hat Red Hat Enterprise Linux 9
- 0:9.9p1-9.el9_8 and laternot affected · rpm
- 0:9.9p1-9.el9_8 and laternot affected · rpm
Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions
- 0:8.7p1-30.el9_2.13 and laternot affected · rpm
Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions
- 0:8.7p1-38.el9_4.10 and laternot affected · rpm
Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support
- 0:8.7p1-45.el9_6.5 and laternot affected · rpm
Red Hat Red Hat Hardened Images
- 10.3p1-6.hum1 and laternot affected · rpm
Red Hat Red Hat OpenShift AI 3.0
- 1791818590 and laternot affected · rpm
- 1791818589 and laternot affected · rpm
- 1791818505 and laternot affected · rpm
- 1791818496 and laternot affected · rpm
- 1791818502 and laternot affected · rpm
- 1793042072 and laternot affected · rpm
Red Hat Red Hat OpenShift AI 3.2
- 1791818602 and laternot affected · rpm
- 1791818598 and laternot affected · rpm
- 1791818512 and laternot affected · rpm
- 1791818587 and laternot affected · rpm
- 1791818778 and laternot affected · rpm
- 1791818512 and laternot affected · rpm
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:10 | openssh | before 9.9p1-25.el10_2.alma.1 | 9.9p1-25.el10_2.alma.1 |
| AlmaLinux:10 | openssh-askpass | before 9.9p1-25.el10_2.alma.1 | 9.9p1-25.el10_2.alma.1 |
| AlmaLinux:10 | openssh-clients | before 9.9p1-25.el10_2.alma.1 | 9.9p1-25.el10_2.alma.1 |
| AlmaLinux:10 | openssh-keycat | before 9.9p1-25.el10_2.alma.1 | 9.9p1-25.el10_2.alma.1 |
| AlmaLinux:10 | openssh-keysign | before 9.9p1-25.el10_2.alma.1 | 9.9p1-25.el10_2.alma.1 |
| AlmaLinux:10 | openssh-server | before 9.9p1-25.el10_2.alma.1 | 9.9p1-25.el10_2.alma.1 |
| AlmaLinux:8 | openssh | before 8.0p1-30.el8_10 | 8.0p1-30.el8_10 |
| AlmaLinux:8 | openssh-askpass | before 8.0p1-30.el8_10 | 8.0p1-30.el8_10 |
| AlmaLinux:8 | openssh-cavs | before 8.0p1-30.el8_10 | 8.0p1-30.el8_10 |
| AlmaLinux:8 | openssh-clients | before 8.0p1-30.el8_10 | 8.0p1-30.el8_10 |
| AlmaLinux:8 | openssh-keycat | before 8.0p1-30.el8_10 | 8.0p1-30.el8_10 |
| AlmaLinux:8 | openssh-ldap | before 8.0p1-30.el8_10 | 8.0p1-30.el8_10 |
| AlmaLinux:8 | openssh-server | before 8.0p1-30.el8_10 | 8.0p1-30.el8_10 |
| AlmaLinux:8 | pam_ssh_agent_auth | before 0.10.3-7.30.el8_10 | 0.10.3-7.30.el8_10 |
| AlmaLinux:9 | openssh | before 9.9p1-9.el9_8.alma.1 | 9.9p1-9.el9_8.alma.1 |
| AlmaLinux:9 | openssh-askpass | before 9.9p1-9.el9_8.alma.1 | 9.9p1-9.el9_8.alma.1 |
| AlmaLinux:9 | openssh-clients | before 9.9p1-9.el9_8.alma.1 | 9.9p1-9.el9_8.alma.1 |
| AlmaLinux:9 | openssh-keycat | before 9.9p1-9.el9_8.alma.1 | 9.9p1-9.el9_8.alma.1 |
| AlmaLinux:9 | openssh-server | before 9.9p1-9.el9_8.alma.1 | 9.9p1-9.el9_8.alma.1 |
| AlmaLinux:9 | pam_ssh_agent_auth | before 0.10.4-7.9.el9_8.alma.1 | 0.10.4-7.9.el9_8.alma.1 |
| Red Hat:enterprise_linux_eus:10.0 | openssh | before 0:9.9p1-7.el10_0.5 | 0:9.9p1-7.el10_0.5 |
| Red Hat:enterprise_linux_eus:10.0 | openssh-askpass | before 0:9.9p1-7.el10_0.5 | 0:9.9p1-7.el10_0.5 |
| Red Hat:enterprise_linux_eus:10.0 | openssh-clients | before 0:9.9p1-7.el10_0.5 | 0:9.9p1-7.el10_0.5 |
| Red Hat:enterprise_linux_eus:10.0 | openssh-keycat | before 0:9.9p1-7.el10_0.5 | 0:9.9p1-7.el10_0.5 |
+65
Same product
openbsd: all recordsOther highest-scoring records for the same primary product.
- CVE-2023-38408The PKCS#11 feature in ssh-agent in OpenSSH before 9.3p2 has an insufficiently trustworthy search path, leading to remote code execution if 63This week
- CVE-2018-15473OpenSSH through 7.7 is prone to a user enumeration vulnerability due to not delaying bailout for an invalid authenticating user until after 60This week
- CVE-2016-6210sshd in OpenSSH before 7.3, when SHA256 or SHA512 are used for user password hashing, uses BLOWFISH hashing on a static password when the us60This week
Published before and after this one in the same product
- ← EarlierCVE-2026-35414Apr 2, 2026 · OpenSSH before 10.3 mishandles the authorized_keys principals option in uncommon scenarios involving a principals list in conjunction with a32Monitor
- ← EarlierCVE-2026-55654Jun 23, 2026 · Openssh: heap out-of-bounds read in red hat enterprise linux versions of openssh gssapi indicator cleanup due to missing null sentinel termination14Monitor
- Later →CVE-2026-55655Jun 23, 2026 · Openssh: local mitm of x11 forwarding via abstract unix socket pre-binding in red hat enterprise linux openssh client versions24Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| azl3 openssh 9.8p1-10 on Azure Linux 3.0 | Release Notes | Microsoft (MSRC) |
| almalinux:openssh | 8.0p1-30.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:openssh-askpass | 8.0p1-30.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:openssh-cavs | 8.0p1-30.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:openssh-clients | 8.0p1-30.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:openssh-keycat | 8.0p1-30.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:openssh-keysign | 9.9p1-25.el10_2.alma.1 · AlmaLinux:10 | Package registry (OSV) |
| almalinux:openssh-ldap | 8.0p1-30.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:openssh-server | 8.0p1-30.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:pam_ssh_agent_auth | 0.10.3-7.30.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| red hat:openssh | 0:10.3p1-6.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssh-askpass | 0:10.3p1-6.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssh-askpass | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:openssh-askpass-debuginfo | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:openssh-cavs | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:openssh-cavs-debuginfo | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:openssh-clients | 0:10.3p1-6.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssh-clients-debuginfo | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:openssh-debuginfo | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:openssh-debugsource | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:openssh-keycat | 0:10.3p1-6.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssh-keycat-debuginfo | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:openssh-keysign | 0:10.3p1-6.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssh-ldap-debuginfo | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:openssh-server | 0:10.3p1-6.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:openssh-server-debuginfo | 0:8.0p1-30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:openssh-sk-dummy | 0:10.3p1-6.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:pam_ssh_agent_auth-debuginfo | 0:0.10.3-7.30.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| rocky linux:openssh | 0:8.0p1-30.el8_10 · Rocky Linux:8 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- In partnershipRed Hat (Aisle.com)
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-26-0436 · Jun 24, 2026(OpenSSH Güvenlik Bildirimi)
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- A user must open a link or visit a page.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-415 · Double FreeCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (19 more)Show less
- access.redhat.com/errata/RHSA-2026:47755
- access.redhat.com/errata/RHSA-2026:47756
- access.redhat.com/errata/RHSA-2026:47757
- access.redhat.com/errata/RHSA-2026:54387
- access.redhat.com/errata/RHSA-2026:58981
- access.redhat.com/errata/RHSA-2026:76748
- access.redhat.com/errata/RHSA-2026:76993
- access.redhat.com/errata/RHSA-2026:80513
- access.redhat.com/errata/RHSA-2026:82749
- access.redhat.com/errata/RHSA-2026:82750
- access.redhat.com/errata/RHSA-2026:82751
- access.redhat.com/errata/RHSA-2026:82752
- access.redhat.com/errata/RHSA-2026:82753
- access.redhat.com/errata/RHSA-2026:82754
- access.redhat.com/errata/RHSA-2026:82755
- access.redhat.com/errata/RHSA-2026:82756
- access.redhat.com/errata/RHSA-2026:82757
- access.redhat.com/errata/RHSA-2026:82758
- access.redhat.com/errata/RHSA-2026:82759
Vendor advisories and official records. Exploit/PoC links are deliberately left out.