CVE-2020-4042 [Medium] | Authentication Bypass in Bareos

Bareos before version 19.2.8 and earlier allows a malicious client to communicate with the director without knowledge of the shared secret if the director allows client initiated connection and connects to the client itself. The malicious client can replay the Bareos director's cram-md5 challenge to the director itself leading to the director responding to the replayed challenge. The response obtained is then a valid reply to the directors original challenge. This is fixed in version 19.2.8.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-27	0.27%	0.18%	-0.08%
2	2025-11-21	0.18%	0.27%	+0.08%
3	2025-11-18	—	0.18%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-27

0.27%

0.18%

-0.08%

2025-11-21

0.18%

0.27%

+0.08%

2025-11-18

—

0.18%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
6.8	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N` 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:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:N) Service keeps running; no real outage angle.	2.2	4.0	[email protected]
6.8	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N` 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:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:N) Service keeps running; no real outage angle.	2.2	4.0	[email protected]
4.3	2.0	MEDIUM	`AV:N/AC:M/Au:N/C:N/I:P/A:N` 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:N) No confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:N) No availability impact.	8.6	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

6.8

3.1

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N 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:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N): Service keeps running; no real outage angle.

2.2

4.0

[email protected]

6.8

3.1

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N 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:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N): Service keeps running; no real outage angle.

2.2

4.0

[email protected]

4.3

2.0

MEDIUM

AV:N/AC:M/Au:N/C:N/I:P/A:N 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:N): No confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:N): No availability impact.

8.6

2.9

[email protected]

OS Trackers for CVE-2020-4042

vendor	priority	summary	link
`alpine`	medium	CVE-2020-4042: 1 source package rows (bareos); 7 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 7, open 0.	https://security.alpinelinux.org/vuln/CVE-2020-4042
`ubuntu`	medium	CVE-2020-4042 medium priority: Ubuntu including 1 source packages (bareos), 17 status rows across 17 suites (bionic, eoan, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 15, needed 1, needs-triage 1.	https://ubuntu.com/security/CVE-2020-4042

Affected software / configurations for CVE-2020-4042

Vendor	Product	Version	Raw CPE
bareos	bareos	<= 19.2.7	cpe:2.3:a:bareos:bareos::::::::
bareos	bareos	19.2.8	cpe:2.3:a:bareos:bareos:19.2.8:pre::::::

References for CVE-2020-4042

URL	Tags
https://bugs.bareos.org/view.php?id=1250	Vendor Advisory
https://github.com/bareos/bareos/security/advisories/GHSA-vqpj-2vhj-h752	Mitigation Third Party Advisory

URL

CVE-2020-4042 | Authentication bypass in Bareos

Exploit prediction scoring system (EPSS) score for CVE-2020-4042

Common vulnerability scoring system (CVSS) metrics for CVE-2020-4042

Weakness enumeration for CVE-2020-4042

OS Trackers for CVE-2020-4042

Affected software / configurations for CVE-2020-4042

References for CVE-2020-4042