CVE-2021-38173

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering...

9.8 CriticalFix available

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering SSH commands using ssh_filter_btrbk.sh in authorized_keys.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: High

Exploit likelihood

3.16%Up 2.1 points since Aug 8, 2021

What each source reports

NVD Score used9.8

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering SSH commands using ssh_filter_btrbk.sh in authorized_keys.

Record: CVE-2021-38173
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0: 7.5 HighAV:N/AC:L/Au:N/C:P/I:P/A:P
Weakness: CWE-77
Updated: 2026-11-02

CVE ListNo score

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering SSH commands using ssh_filter_btrbk.sh in authorized_keys.

Record: CVE-2021-38173
Updated: 2026-11-02

EUVDEUVD-2021-24643No score

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering SSH commands using ssh_filter_btrbk.sh in authorized_keys.

Record: EUVD-2021-24643
Updated: 2026-11-03

GitHub AdvisoriesGHSA-c38g-xjq6-3v469.8

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering...

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering SSH commands using ssh_filter_btrbk.sh in authorized_keys.

Record: GHSA-c38g-xjq6-3v46
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-77
Updated: 2026-11-02

OSV9.8

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering SSH commands using ssh_filter_btrbk.sh in authorized_keys.

Record: CVE-2021-38173
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVDEBIAN-CVE-2021-381739.8

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering SSH commands using ssh_filter_btrbk.sh in authorized_keys.

Record: DEBIAN-CVE-2021-38173
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-381739.8

Btrbk before 0.31.2 allows command execution because of the mishandling of remote hosts filtering SSH commands using ssh_filter_btrbk.sh in authorized_keys.

Record: UBUNTU-CVE-2021-38173
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-12

OSVUSN-9049-1No score

btrbk vulnerability

It was discovered that btrbk incorrectly filtered SSH commands received from remote hosts. A remote attacker could possibly use this issue to execute arbitrary commands.

Record: USN-9049-1
Updated: 2026-11-12

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`btrbk` Debian:12	before 0.27.1-2	0.27.1-2
`btrbk` Debian:13	before 0.27.1-2	0.27.1-2
`btrbk` Debian:14	before 0.27.1-2	0.27.1-2
`btrbk` Debian:9	before 0.24.0-1+deb9u1, plus listed versions 0.24.0-1	0.24.0-1+deb9u1
`btrbk` Ubuntu:Pro:18.04:LTS	before 0.26.0-1ubuntu0.1~esm1, plus listed versions 0.25.1-10.26.0-1	0.26.0-1ubuntu0.1~esm1
`btrbk` Ubuntu:Pro:20.04:LTS	before 0.27.1-1ubuntu0.1~esm1, plus listed versions 0.27.1-1	0.27.1-1ubuntu0.1~esm1

History

History
Recorded	Changed	Sources
Nov 12, 2026	affected, aliases, facts, references	OSV
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-38173 is a critical vulnerability (CVSS 9.8) in Digint Btrbk, published August 7, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.16%, the 88th percentile. Fixed in btrbk 0.27.1-2.

References

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