VulnerabilityPublished 9 Mar 2026Updated 11 Mar 2026

CVE-2026-3731: libssh · Out-of-bounds Read

Affects libsshSource CVE Database V5

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Not known to be exploited · CVSS 6.9 Medium.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score

6.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 51% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

usn-8093-1

What to do

Affected software

Product	Affected	Fixed in
libssh	Affected 0.11.0 – 0.11.3 4 affected builds	Fixed in–
GitHublibssh/libssh`pkg:github/libssh/libssh`Other threats	Affected 0.11.0 – 0.11.3 4 affected builds	Fixed in–

CPE configurations (1)

cpe:2.3:a:libssh:libssh:*:*:*:*:*:*:*:*

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AI-suggested

Organizations should immediately upgrade libssh to versions 0.11.4 or 0.12.0 to remediate this vulnerability. Beyond upgrading, administrators should audit their environments to identify all instances of libssh usage, including embedded devices and network appliances, to ensure comprehensive patching. Employ network-level protections such as firewall rules to restrict SSH/SFTP access to trusted IP ranges, reducing exposure to remote attacks. Monitoring and logging SSH/SFTP traffic for anomalous behavior may help detect exploitation attempts. For environments where immediate upgrading is not feasible, consider disabling or restricting SFTP extensions if possible, or deploying application-layer proxies that can filter malformed requests. Regularly review vendor advisories for updates or additional patches related to libssh. Finally, incorporate this vulnerability into vulnerability management and incident response plans to ensure timely detection and remediation.

Description

A weakness has been identified in libssh up to 0.11.3. The impacted element is the function sftp_extensions_get_name/sftp_extensions_get_data of the file src/sftp.c of the component SFTP Extension Name Handler. Executing a manipulation of the argument idx can lead to out-of-bounds read. The attack may be performed from remote. Upgrading to version 0.11.4 and 0.12.0 is sufficient to resolve this issue. This patch is called 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60. You should upgrade the affected component.

Impact

The primary impact of CVE-2026-3731 is the potential for remote attackers to cause out-of-bounds memory reads in applications using vulnerable libssh versions. This can lead to information disclosure if sensitive memory contents are exposed or to denial of service if the application crashes. Since libssh is widely used in SSH and SFTP implementations across various platforms, the vulnerability could affect numerous servers and network devices globally. Attackers could leverage this flaw to gain insights into memory layout or extract sensitive data, which might facilitate further attacks. The lack of authentication or user interaction requirements lowers the barrier for exploitation, increasing the threat to exposed services. While no active exploits are currently reported, the vulnerability's characteristics suggest that attackers could develop reliable exploits, especially targeting high-value infrastructure relying on libssh.

Summary

CVE-2026-3731 identifies a vulnerability in the libssh library, specifically in versions 0.11.0 through 0.11.3, within the SFTP extension name handler component. The affected functions, sftp_extensions_get_name and sftp_extensions_get_data, improperly validate the 'idx' argument, which is used to index into internal data structures representing SFTP extensions. This improper validation can lead to an out-of-bounds read, where memory outside the intended buffer is accessed. Such out-of-bounds reads can cause application crashes or potentially leak sensitive memory contents, depending on the context and memory layout. The vulnerability is exploitable remotely without requiring authentication or user interaction, increasing its risk profile. The flaw was addressed by a patch (commit 855a0853ad3abd4a6cd85ce06fce6d8d4c7a0b60) that properly validates the index before accessing memory. Upgrading to libssh versions 0.11.4 or 0.12.0 resolves the issue. Although no public exploits are known, the vulnerability's remote nature and lack of prerequisites make it a significant concern for systems relying on libssh for secure shell or SFTP operations.

References

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