Low [CVE-2025-8277] Libssh: memory exhaustion via repeated key exchange in libssh
This low-severity Red Hat Linux advisory covers CVE-2025-8277 affecting Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6.
Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.
VulniPulse record published
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.
The Red Hat Product Security team has assessed the severity of this vulnerability as Low.The issue requires an authenticated client to repeatedly initiate key exchanges with incorrect guesses, which leads to memory not being properly released.
While this flaw can result in gradual memory exhaustion and potential denial of service (DoS) on the client side, it is not easily exploitable in typical usage scenarios and does not affect servers. The vulnerability does not compromise confidentiality or integrity and poses limited impact on system availability under normal operating conditions.
Weakness: CWE-401. Affected Red Hat products: Red Hat Enterprise Linux 9; Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat OpenShift Container Platform 4.
Will not fix / out of support: Red Hat Enterprise Linux 6. Red Hat fixing advisory: RHSA-2026:18683.
Affected products named by the advisory: Red Hat package: libssh2.
Is CVE-2025-8277 exploited?
No exploitation is reported in the sources VulniPulse tracks: CVE-2025-8277 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.
How do I fix CVE-2025-8277?
Upgrade to a fixed release named by Red Hat:
- libssh-0:0.10.4-18.el9
- RHSA-2026:18683
Confirm against the vendor advisory before you patch.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
- libssh-0:0.10.4-18.el9
- RHSA-2026:18683
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. It is strongly advised to apply updated libssh packages once available to prevent memory exhaustion risks on client systems.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
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