CVE-2021-28041

ssh-agent in OpenSSH before 8.5 has a double free that may be relevant in a few less-common scenarios, such as unconstrained agent-socket access on a legacy operating system, or the forwarding of an agent to an attacker-controlled host.

Published: 2021-03-05 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-28041 is rated Moderate Risk (45.6/100): CVSS High severity, with low exploitation likelihood (EPSS 0.26%). Review affected assets and schedule 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-2021-28041

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 2026-05-27 0.24% 0.26% +0.02%
2 2026-02-09 0.30% 0.24% -0.06%
3 2026-02-04 — 0.30% —

Full EPSS history (40 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-28041

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.1 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:L/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:L)
A normal user session is enough; they don’t have to be admin.
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.
 1.2 5.9 [email protected]
4.6 2.0 MEDIUM
AV:N/AC:H/Au:S/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:H)
Exploitation requires uncommon or highly specific conditions.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 3.9 6.4 [email protected]

Weakness enumeration for CVE-2021-28041

OS Trackers for CVE-2021-28041

vendor priority summary link
alpine high CVE-2021-28041: 1 source package rows (openssh); 36 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 9, open 27. https://security.alpinelinux.org/vuln/CVE-2021-28041
debian not yet assigned CVE-2021-28041 not yet assigned priority: Debian including 1 source packages (openssh), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-28041
gentoo normal CVE-2021-28041: 1 GLSA(s) (202105-35), 1 atom(s) (net-misc/openssh); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-28041
redhat medium — https://access.redhat.com/security/cve/CVE-2021-28041
suse high CVE-2021-28041 severity important: SUSE including 359 source package names (0.7.1-rev1.0.0-build2.2.1:openssh-8.4p1-3.9.1, 0.7.1-rev1.0.0-build2.2.1:openssh-clients-8.4p1-3.9.1, …), 1284 product×package rows across 281 product lines (Container bci/golang, Container bci/nodejs, … (281 product lines)): Fixed 988, Known Affected 175, Known Not Affected 121. https://www.suse.com/security/cve/CVE-2021-28041/
ubuntu medium CVE-2021-28041 medium priority: Ubuntu including 2 source packages (openssh, openssh-ssh1), 12 status rows across 6 suites (bionic, focal, groovy, trusty, upstream, xenial): not-affected 6, DNE 2, released 2, ignored 1, needs-triage 1. https://ubuntu.com/security/CVE-2021-28041

Affected software / configurations for CVE-2021-28041

Vendor Product Version Raw CPE
openbsd openssh >= 8.2, < 8.5 cpe:2.3:a:openbsd:openssh:*:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
netapp cloud_backup — cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*
netapp hci_management_node — cpe:2.3:a:netapp:hci_management_node:-:*:*:*:*:*:*:*
netapp solidfire — cpe:2.3:a:netapp:solidfire:-:*:*:*:*:*:*:*
netapp hci_compute_node_firmware — cpe:2.3:o:netapp:hci_compute_node_firmware:-:*:*:*:*:*:*:*
netapp hci_storage_node_firmware — cpe:2.3:o:netapp:hci_storage_node_firmware:-:*:*:*:*:*:*:*
oracle communications_offline_mediation_controller 12.0.0.3.0 cpe:2.3:a:oracle:communications_offline_mediation_controller:12.0.0.3.0:*:*:*:*:*:*:*
oracle zfs_storage_appliance 8.8 cpe:2.3:o:oracle:zfs_storage_appliance:8.8:*:*:*:*:*:*:*

References for CVE-2021-28041

URL Tags
https://github.com/openssh/openssh-portable/commit/e04fd6dde16de1cdc5a4d9946397ff60d96568db Patch Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KQWGII3LQR4AOTPPFXGMTYE7UDEWIUKI/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TXST2CML2MWY3PNVUXX7FFJE3ATJMNVZ/
https://security.gentoo.org/glsa/202105-35 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210416-0002/ Third Party Advisory
https://www.openssh.com/security.html Not Applicable Vendor Advisory
https://www.openssh.com/txt/release-8.5 Release Notes Vendor Advisory
https://www.openwall.com/lists/oss-security/2021/03/03/1 Mailing List Patch Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html Third Party Advisory
cvelogic Threat Intelligence