Platform
linux
Component
openssh
Fixed in
10.3
CVE-2026-35387 describes a vulnerability in OpenSSH where the software incorrectly handles ECDSA (Elliptic Curve Digital Signature Algorithm) algorithm specifications. This misinterpretation allows an attacker to potentially influence the algorithms used during authentication, bypassing intended restrictions. The vulnerability impacts OpenSSH versions from 0.0 through 10.3, and a fix is available in version 10.3.
The core of the vulnerability lies in how OpenSSH parses the PubkeyAcceptedAlgorithms and HostbasedAcceptedAlgorithms configuration options. Instead of strictly enforcing the listed algorithms, OpenSSH before version 10.3 interprets any ECDSA algorithm listed as an implicit acceptance of all ECDSA algorithms. This means an attacker could potentially specify an ECDSA algorithm that is not intended to be accepted, effectively bypassing authentication controls. While the CVSS score is LOW, the potential impact is significant as it could lead to unauthorized access to systems protected by OpenSSH. A successful exploitation could allow an attacker to establish connections using weaker or compromised ECDSA keys, potentially leading to data breaches or system compromise. The blast radius is limited to systems directly using OpenSSH for authentication, but the widespread use of OpenSSH makes this a relevant concern for many organizations.
CVE-2026-35387 was published on April 2, 2026. Its CVSS score is LOW, indicating a relatively low probability of exploitation. There are currently no publicly known proof-of-concept exploits available. The vulnerability is not listed on KEV (Kernel Exploitability Vulnerability) or EPSS (Exploit Prediction Scoring System) as of this writing. While no active campaigns are known, the potential for bypassing authentication controls warrants prompt remediation.
Exploit Status
EPSS
0.03% (9% percentile)
CISA SSVC
CVSS Vector
The primary mitigation for CVE-2026-35387 is to upgrade to OpenSSH version 10.3 or later. This version corrects the parsing logic and enforces the intended algorithm restrictions. If upgrading is not immediately feasible, consider temporarily restricting the ECDSA algorithms allowed in the PubkeyAcceptedAlgorithms and HostbasedAcceptedAlgorithms configuration files to only those absolutely necessary. This limits the attack surface by preventing the use of less common or potentially vulnerable ECDSA curves. Additionally, review your OpenSSH configuration to ensure that only trusted keys are authorized. After upgrading, confirm the fix by attempting to connect using an ECDSA key with an algorithm not explicitly listed in the configuration; the connection should be rejected.
Actualice OpenSSH a la versión 10.3 o posterior. Esto corregirá la interpretación incorrecta de los algoritmos ECDSA en las configuraciones PubkeyAcceptedAlgorithms o HostbasedAcceptedAlgorithms.
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It's a vulnerability in OpenSSH where the software incorrectly handles ECDSA algorithm specifications, potentially allowing unintended algorithms to be used during authentication.
If you are running OpenSSH versions 0.0 through 10.2, you are potentially affected. Upgrade to version 10.3 or later to mitigate the risk.
The recommended fix is to upgrade to OpenSSH version 10.3 or later. If immediate upgrade is not possible, restrict ECDSA algorithms in your configuration.
As of now, there are no publicly known exploits or active campaigns targeting this vulnerability, but proactive patching is still recommended.
Refer to the official OpenSSH security advisory and the NVD (National Vulnerability Database) entry for CVE-2026-35387 for detailed information.
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