VulnerabilityPublished 7 Nov 2023Updated 29 Sep 2025

CVE-2023-47102: UrBackup Server · Observable Discrepancy

Source CVE Database V5

Not known to be exploited · CVSS 5.3 Medium.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 7 Nov 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

AI-suggested

To mitigate CVE-2023-47102, organizations should implement the following specific measures: 1) Configure UrBackup Server to use generic authentication failure messages that do not reveal whether a username is valid or invalid, thereby preventing username enumeration. 2) Enforce strong password policies and account lockout thresholds to limit the effectiveness of brute-force attacks following username enumeration. 3) Monitor authentication logs for repeated failed login attempts and implement alerting to detect potential enumeration or brute-force activity. 4) Restrict network access to the UrBackup Server management interface to trusted IP addresses or VPNs to reduce exposure to external attackers. 5) If possible, upgrade to a patched version once available or apply vendor-recommended workarounds. 6) Employ multi-factor authentication (MFA) for user accounts to add an additional layer of security beyond passwords. 7) Regularly audit user accounts and remove or disable unused accounts to minimize the attack surface. These targeted mitigations go beyond generic advice by focusing on configuration changes, monitoring, and access controls specific to the nature of this vulnerability.

Description

UrBackup Server 2.5.31 allows brute-force enumeration of user accounts because a failure message confirms that a username is not valid.

Impact

For European organizations using UrBackup Server 2.5.31, this vulnerability poses a risk primarily to the confidentiality of user account information. By enabling attackers to enumerate valid usernames remotely without authentication or user interaction, it lowers the barrier for subsequent targeted attacks such as brute-force password attempts, phishing, or credential stuffing. Organizations relying on UrBackup for backup and recovery services could face increased risk of unauthorized access if attackers combine username enumeration with weak password policies. Although the vulnerability does not directly allow data modification or denial of service, the exposure of valid usernames can facilitate lateral movement or privilege escalation in complex environments. Given that backup servers often hold critical data and access credentials, this reconnaissance capability could be a stepping stone for more damaging attacks. European entities with compliance obligations under GDPR must consider the potential for indirect data breaches resulting from compromised accounts. The lack of known exploits suggests limited immediate threat, but proactive mitigation is advisable to prevent exploitation.

CWE-203Observable Discrepancy (opens in a new tab)
Base weakness
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
Implementation
Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended).
OWASP Cheat Sheets
Error Handling (opens in a new tab)
Logging (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.4 (opens in a new tab)
V14.3.3 (opens in a new tab)
V7.3.3 (opens in a new tab)
Attack patterns
Black Box Reverse Engineering (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 4 Oct 2025, 10:19 UTC

WeaknessesCWE-203

Technical details

References

Community reviews

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