Libssh: memory exhaustion via repeated key exchange in libssh
Priority LOW 16CWE-401Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- High
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Partial Red Hat: 2 fixed, 5 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-401.
Summary
A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00431 37th percentileScored 2026-11-07
Fix Partial libssh: 0.11.3Red Hat: 1 advisoryRed Hat: 2 fixed, 5 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | libssh | 0.6.0 to before 0.11.3 | 0.11.3 | Patch available | CNA |
| Red Hat | Red Hat Enterprise Linux 9 | — | 0.10.4-18.el9 | Patch available | CNA |
| Red Hat | Red Hat Enterprise Linux 9 | — | 0.10.4-18.el9 | Patch available | CNA |
| Red Hat | Red Hat Enterprise Linux 10 | — | — | No fix listed | CNA |
| Red Hat | Red Hat Enterprise Linux 6 | — | — | No fix listed | CNA |
| Red Hat | Red Hat Enterprise Linux 7 | — | — | No fix listed | CNA |
| Red Hat | Red Hat Enterprise Linux 8 | — | — | No fix listed | CNA |
| Red Hat | Red Hat OpenShift Container Platform 4 | — | — | No fix listed | CNA |
| Red Hat | Red Hat OpenShift Container Platform 4 | — | — | No fix listed | CNA |
- libssh Vendor— Affected 0.6.0 to before 0.11.3 Fixed in 0.11.3 Patch available CNA
- Red Hat Enterprise Linux 9 VendorRed Hat Affected — Fixed in 0.10.4-18.el9 Patch available CNA
- Red Hat Enterprise Linux 9 VendorRed Hat Affected — Fixed in 0.10.4-18.el9 Patch available CNA
- Red Hat Enterprise Linux 10 VendorRed Hat Affected — Fixed in — No fix listed CNA
- Red Hat Enterprise Linux 6 VendorRed Hat Affected — Fixed in — No fix listed CNA
- Red Hat Enterprise Linux 7 VendorRed Hat Affected — Fixed in — No fix listed CNA
- Red Hat Enterprise Linux 8 VendorRed Hat Affected — Fixed in — No fix listed CNA
- Red Hat OpenShift Container Platform 4 VendorRed Hat Affected — Fixed in — No fix listed CNA
- Red Hat OpenShift Container Platform 4 VendorRed Hat Affected — Fixed in — No fix listed CNA
CPE names CNA · 7
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:/a:redhat:enterprise_linux:9::appstream | 9 | — | Red Hat |
| cpe:/o:redhat:enterprise_linux:9::baseos | 9 | — | Red Hat |
| cpe:/a:redhat:enterprise_linux:10 | 10 | — | Red Hat |
| cpe:/o:redhat:rhel_els:6 | 6 | — | Red Hat |
| cpe:/o:redhat:rhel_els:7 | 7 | — | Red Hat |
| cpe:/a:redhat:enterprise_linux:8 | 8 | — | Red Hat |
| cpe:/a:redhat:openshift:4 | 4 | — | Red Hat |
- cpe:/a:redhat:enterprise_linux:9::appstream Versions 9 — ·Red Hat
- cpe:/o:redhat:enterprise_linux:9::baseos Versions 9 — ·Red Hat
- cpe:/a:redhat:enterprise_linux:10 Versions 10 — ·Red Hat
- cpe:/o:redhat:rhel_els:6 Versions 6 — ·Red Hat
- cpe:/o:redhat:rhel_els:7 Versions 7 — ·Red Hat
- cpe:/a:redhat:enterprise_linux:8 Versions 8 — ·Red Hat
- cpe:/a:redhat:openshift:4 Versions 4 — ·Red Hat
Remediation
- Fix · CNA libssh Fixed in 0.11.3
Red Hat 1 advisory
- RHSA-2026:18683 Released 2026-05-19 · Red Hat rating Moderatelibssh security update
- Red Hat Enterprise Linux AppStream (v. 9) libssh-devel-0.10.4-18.el9
- Red Hat Enterprise Linux BaseOS (v. 9) libssh-0.10.4-18.el9, libssh-config-0.10.4-18.el9
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux AppStream (v. 9) | Fixed | RHSA-2026:18683 |
| Red Hat Enterprise Linux BaseOS (v. 9) | Fixed | RHSA-2026:18683 |
Timeline
- 2026-10-02 Threatist record created from CVE-2025-8277
- 2026-10-03 Alias added: GHSA-39mw-228p-wr6v
References
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Sources
- CVE-2025-8277 · CVE Program
- CVE-2025-8277 · NVD
- FIRST EPSS
- GHSA-39mw-228p-wr6v · GitHub Advisory Database · CC BY 4.0
- CVE-2025-8277 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences