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libssh EUVDEUVD-2026-46176

| CVE-2026-59842 MEDIUM
Out-of-bounds Read (CWE-125)
2026-07-21 redhat GHSA-x94w-cg8g-g593
Buffer Overflow Information Disclosure Microsoft Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 9 Red Hat Hardened Images Red Hat
5.3
CVSS 3.1 · NVD
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Severity by source

Vendor (redhat) PRIMARY
LOW
qualitative
NVD
5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
vuln.today AI
3.7 LOW

GSSAPI key exchange must be explicitly enabled (AC:H); attack is pre-authentication (PR:N) with only small, bounded memory disclosure (C:L) and no integrity or availability impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
SUSE
3.7 LOW
AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Red Hat
3.7 LOW
qualitative

Primary rating from Vendor (redhat).

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

Lifecycle Timeline

4
Severity Changed
Jul 30, 2026 - 13:22 NVD
LOW MEDIUM
CVSS changed
Jul 30, 2026 - 13:22 NVD
3.7 (LOW) 5.3 (MEDIUM)
Analysis Generated
Jul 21, 2026 - 12:01 vuln.today
CVE Published
Jul 21, 2026 - 11:08 cve.org
LOW 3.7

DescriptionNVD

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

AnalysisAI

Out-of-bounds heap read in libssh exposes small amounts of server memory during GSSAPI key exchange, exploitable by remote unauthenticated attackers. When a client submits a Curve25519 public key shorter than the expected 32 bytes during server-side GSSAPI key exchange, libssh copies the key without validating its length, triggering a read beyond the intended buffer boundary. No public exploit has been identified at time of analysis; exploitation is constrained to servers with GSSAPI key exchange explicitly enabled, which is a non-default configuration.

Technical ContextAI

libssh is a multiplatform C library implementing the SSHv2 protocol, widely packaged in enterprise Linux distributions. The flaw resides in the server-side GSSAPI (Generic Security Services Application Program Interface) key exchange routine, specifically in Curve25519 ECDH public key ingestion. CWE-125 (Out-of-bounds Read) identifies the root cause: the library performs a heap memory copy of the client-supplied Curve25519 key without first asserting that the input meets the mandatory 32-byte length. The under-length key causes the copy to read adjacent heap memory beyond the buffer, potentially exposing nearby heap contents. Per CPE data, affected products include libssh as packaged in Red Hat Enterprise Linux 8 (cpe:2.3:a:red_hat:red_hat_enterprise_linux_8), RHEL 9, RHEL 10, and Red Hat Hardened Images.

RemediationAI

An exact fixed libssh package version is not confirmed in the available intelligence - monitor the Red Hat Security Advisory at https://access.redhat.com/security/cve/CVE-2026-59842 and Bugzilla issue 2498168 for patch release. On RHEL 8, 9, and 10 systems, apply errata updates via 'dnf update libssh' once Red Hat publishes a patched package. As an immediate compensating control, disable GSSAPI key exchange in the libssh server configuration if not operationally required; this eliminates the vulnerable code path entirely with no impact to non-GSSAPI SSH sessions. Additionally, restricting SSH server access to trusted networks via host-based firewall rules (e.g., firewalld or iptables) reduces exposure to untrusted clients while a patch is pending.

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Same weakness CWE-125 – Out-of-bounds Read

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Same technique Buffer Overflow

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Vendor StatusVendor

SUSE

Severity: Low
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Not-Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Not-Affected
SUSE Linux Enterprise Micro 5.3 Not-Affected
SUSE Linux Enterprise Micro 5.4 Not-Affected
SUSE Linux Enterprise Micro 5.5 Not-Affected

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EUVD-2026-46176 vulnerability details – vuln.today
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