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Fencer Vulns
high 7.1

CVE-2021-28041 json

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 a…

published 2021-03-05 5 y ago modified 2026-10-14 26 d ago also EUVD-2021-14748 , JLSEC-2026-64

cvss
7.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.5%
EPSS 3.5% chance of exploitation in 30 days, percentile 89%
public exploits
0
none known

Summary

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.

Patch / fix

  • julia OpenSSH_jll 9.1.0+0
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • openssh Debian 14, Debian 13, Debian 12 1:8.4p1-5

debian advisories DEBIAN-CVE-2021-28041

  • openssh Ubuntu 20.04 LTS 1:8.2p1-4ubuntu0.2

ubuntu advisories UBUNTU-CVE-2021-28041

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openssh SLE Module for Server Applications 15 SP3, SLE Module for Basesystem 15 SP3, SLE Micro 5.1 8.4p1-3.9.1
  • openssh-askpass-gnome SLE Module for Desktop Applications 15 SP3 8.4p1-3.9.1

suse advisories SUSE-SU-2021:4153-1

  • openssh openSUSE Tumbleweed 9.6p1-3.1
  • openssh openSUSE Leap 15.3 8.4p1-3.9.1
  • openssh-askpass-gnome openSUSE Leap 15.3 8.4p1-3.9.1

opensuse advisories openSUSE-SU-2024:13842-1openSUSE-SU-2021:4153-1

  • openssh Alpine 3.12 8.3_p1-r2
  • openssh Alpine 3.13 8.4_p1-r1
  • openssh Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 8.5_p1-r0

alpine advisories ALPINE-CVE-2021-28041

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openssh Arch Linux 8.5p1-1

arch linux advisories AVG-1657

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-28041 updated cvss 7.1

openssh: double-free memory corruption may lead to arbitrary code execution

  • Red Hat Enterprise Linux 6 openssh, openssh-ldap, openssh-server, openssh-askpass, openssh-clients, pam_ssh_agent_auth Red Hat Enterprise Linux 7 openssh, openssh-cavs, openssh-ldap, openssh-keycat, openssh-server, openssh-askpass, +3 more Red Hat Enterprise Linux 8 openssh, openssh-cavs, openssh-ldap, openssh-keycat, openssh-server, openssh-askpass, +2 more Red Hat Enterprise Linux 9 openssh, openssh-keycat, openssh-server, openssh-askpass, openssh-clients, pam_ssh_agent_auth
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-23-348-10 updated cvss 7.1

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

3.51% chance of exploitation in the next 30 days, higher than 89% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
NVD 2.0 4.6 AV:N/AC:H/Au:S/C:P/I:P/A:P
OSV 3.1 7.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
julia OpenSSH_jll
>=8.9.0+0, <9.1.0+0
9.1.0+0

Affected products

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.