CVE-2019-3855

An integer overflow flaw which could lead to an out of bounds write was discovered in libssh2 before 1.8.1 in the way packets are read from the server. A remote attacker who compromises a SSH server may be able to execute code on the client system when a user connects to the server.

Published: 2019-03-21 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2019-3855 is rated Moderate Risk (63.3/100): CVSS High severity, with high exploitation likelihood (EPSS 9.22%, 95th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2019-3855

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 16.24% 9.22% -7.02%
2 2026-03-30 13.00% 16.24% +3.24%
3 2026-03-13 — 13.00% —

Full EPSS history (39 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2019-3855

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
7.5 3.0 HIGH
CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.6 5.9 [email protected]
9.3 2.0 HIGH
AV:N/AC:M/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 8.6 10.0 [email protected]

Weakness enumeration for CVE-2019-3855

OS Trackers for CVE-2019-3855

vendor priority summary link
alpine high CVE-2019-3855: 1 source package rows (libssh2); 10 state rows across 10 repos (3.10-main, 3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 10, open 0. https://security.alpinelinux.org/vuln/CVE-2019-3855
debian not yet assigned CVE-2019-3855 not yet assigned priority: Debian including 1 source packages (libssh2), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2019-3855
redhat high — https://access.redhat.com/security/cve/CVE-2019-3855
suse medium CVE-2019-3855 severity moderate: SUSE including 384 source package names (0.38.1.5.8.40:libssh2-1-1.9.0-4.13.1, 0.38.1.5.8.45:libssh2-1-1.9.0-4.13.1, …), 495 product×package rows across 88 product lines (Container caasp/v4/nginx-ingress-controller, Container suse/sles/15.2/virt-handler, … (88 product lines)): Fixed 234, Known Affected 231, Known Not Affected 30. https://www.suse.com/security/cve/CVE-2019-3855/
ubuntu medium CVE-2019-3855 medium priority: Ubuntu including 1 source packages (libssh2), 19 status rows across 19 suites (bionic, cosmic, disco, eoan, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 14, released 2, ignored 1, needed 1, needs-triage 1. https://ubuntu.com/security/CVE-2019-3855

Affected software / configurations for CVE-2019-3855

Vendor Product Version Raw CPE
libssh2 libssh2 < 1.8.1 cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*
fedoraproject fedora 28 cpe:2.3:o:fedoraproject:fedora:28:*:*:*:*:*:*:*
fedoraproject fedora 29 cpe:2.3:o:fedoraproject:fedora:29:*:*:*:*:*:*:*
fedoraproject fedora 30 cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*
debian debian_linux 8.0 cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
netapp ontap_select_deploy_administration_utility — cpe:2.3:a:netapp:ontap_select_deploy_administration_utility:-:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:advanced_virtualization:*:*:*
redhat enterprise_linux_desktop 7.0 cpe:2.3:o:redhat:enterprise_linux_desktop:7.0:*:*:*:*:*:*:*
redhat enterprise_linux_server 7.0 cpe:2.3:o:redhat:enterprise_linux_server:7.0:*:*:*:*:*:*:*
redhat enterprise_linux_server_aus 7.6 cpe:2.3:o:redhat:enterprise_linux_server_aus:7.6:*:*:*:*:*:*:*
redhat enterprise_linux_server_eus 7.6 cpe:2.3:o:redhat:enterprise_linux_server_eus:7.6:*:*:*:*:*:*:*
redhat enterprise_linux_server_tus 7.6 cpe:2.3:o:redhat:enterprise_linux_server_tus:7.6:*:*:*:*:*:*:*
redhat enterprise_linux_workstation 7.0 cpe:2.3:o:redhat:enterprise_linux_workstation:7.0:*:*:*:*:*:*:*
opensuse leap 42.3 cpe:2.3:o:opensuse:leap:42.3:*:*:*:*:*:*:*
apple xcode < 11.0 cpe:2.3:a:apple:xcode:*:*:*:*:*:*:*:*
oracle peoplesoft_enterprise_peopletools 8.56 cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.56:*:*:*:*:*:*:*
oracle peoplesoft_enterprise_peopletools 8.57 cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.57:*:*:*:*:*:*:*

References for CVE-2019-3855

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2019-03/msg00040.html Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00003.html Third Party Advisory
http://packetstormsecurity.com/files/152136/Slackware-Security-Advisory-libssh2-Updates.html Third Party Advisory VDB Entry
http://seclists.org/fulldisclosure/2019/Sep/42 Mailing List Third Party Advisory
http://www.openwall.com/lists/oss-security/2019/03/18/3 Mailing List Patch Third Party Advisory
http://www.securityfocus.com/bid/107485 Third Party Advisory VDB Entry
https://access.redhat.com/errata/RHSA-2019:0679 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1175 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1652 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1791 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1943 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2399 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-3855 Issue Tracking Patch Third Party Advisory
https://lists.debian.org/debian-lts-announce/2019/03/msg00032.html Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5DK6VO2CEUTAJFYIKWNZKEKYMYR3NO2O/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6LUNHPW64IGCASZ4JQ2J5KDXNZN53DWW/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M7IF3LNHOA75O4WZWIHJLIRMA5LJUED3/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XCWEA5ZCLKRDUK62QVVYMFWLWKOPX3LO/
https://seclists.org/bugtraq/2019/Apr/25 Mailing List Third Party Advisory
https://seclists.org/bugtraq/2019/Mar/25 Mailing List Third Party Advisory
https://seclists.org/bugtraq/2019/Sep/49 Mailing List Third Party Advisory
https://security.netapp.com/advisory/ntap-20190327-0005/ Third Party Advisory
https://support.apple.com/kb/HT210609 Third Party Advisory
https://www.broadcom.com/support/fibre-channel-networking/security-advisories/brocade-security-advisory-2019-767 Third Party Advisory
https://www.debian.org/security/2019/dsa-4431 Third Party Advisory
https://www.libssh2.org/CVE-2019-3855.html Patch Vendor Advisory
https://www.oracle.com/technetwork/security-advisory/cpuoct2019-5072832.html Patch Third Party Advisory
cvelogic Threat Intelligence