Common Weakness Enumeration
CWE-204
AllowedObservable Response Discrepancy
Abstraction: Base · Status: Incomplete
The product provides different responses to incoming requests in a way that reveals internal state information to an unauthorized actor outside of the intended control sphere.
203 vulnerabilities reference this CWE, most recent first.
CVE-2019-25338 (GCVE-0-2019-25338)
Vulnerability from cvelistv5 – Published: 2026-02-12 22:48 – Updated: 2026-03-05 01:26
VLAI
EPSS
VEX
Title
Dokuwiki 2018-04-22b - Username Enumeration
Summary
DokuWiki 2018-04-22b contains a username enumeration vulnerability in its password reset functionality that allows attackers to identify valid user accounts. Attackers can submit different usernames to the password reset endpoint and distinguish between existing and non-existing accounts by analyzing the server's error response messages.
Severity
5.3 (Medium)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-02-13 17:05 UTC
CWE
- CWE-204 - Observable Response Discrepancy
Assigner
VulnCheck
CNA
References
4 references
| URL | Tags |
|---|---|
| https://www.exploit-db.com/exploits/47731 | exploit |
| https://www.dokuwiki.org/dokuwiki | product |
| https://download.dokuwiki.org/ | product |
| https://www.vulncheck.com/advisories/dokuwiki-b-u… | third-party-advisory |
Impacted products
Date Public
2019-12-01 00:00
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CVE-2018-25350 (GCVE-0-2018-25350)
Vulnerability from cvelistv5 – Published: 2026-05-23 18:30 – Updated: 2026-05-26 13:27
VLAI
EPSS
VEX
Title
userSpice 4.3.24 Username Enumeration via existingUsernameCheck.php
Summary
userSpice 4.3.24 contains a username enumeration vulnerability that allows unauthenticated attackers to discover valid usernames by sending POST requests to the existingUsernameCheck.php endpoint. Attackers can submit usernames and analyze response text for the 'taken' string to identify existing accounts in the system.
Severity
9.8 (Critical)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-26 13:27 UTC
CWE
- CWE-204 - Observable Response Discrepancy
Assigner
VulnCheck
CNA
References
2 references
| URL | Tags |
|---|---|
| https://www.exploit-db.com/exploits/44872 | exploit |
| https://www.vulncheck.com/advisories/userspice-us… | third-party-advisory |
Date Public
2018-06-10 00:00
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CVE-2016-9499 (GCVE-0-2016-9499)
Vulnerability from cvelistv5 – Published: 2018-07-13 20:00 – Updated: 2024-08-06 02:50
VLAI
EPSS
VEX
Title
The Accellion FTP server prior to version FTA_9_12_220 is vulnerable to cross-site scripting.
Summary
Accellion FTP server prior to version FTA_9_12_220 only returns the username in the server response if the username is invalid. An attacker may use this information to determine valid user accounts and enumerate them.
Severity
No CVSS data available.
CWE
Assigner
certcc
CNA
References
3 references
| URL | Tags |
|---|---|
| https://www.qualys.com/2016/12/06/qsa-2016-12-06/… | x_refsource_MISC |
| https://www.securityfocus.com/bid/96154 | vdb-entryx_refsource_BID |
| https://www.kb.cert.org/vuls/id/745607 | third-party-advisoryx_refsource_CERT-VN |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Accellion | FTP Server |
Affected:
FTA_9_12_220 , < FTA_9_12_220
(custom)
|
Date Public
2017-02-08 00:00
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Mitigation MIT-46
Architecture and Design
Strategy: 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.
- Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Mitigation MIT-39
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). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success.
- If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files.
- Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.
CAPEC-331: ICMP IP Total Length Field Probe
An adversary sends a UDP packet to a closed port on the target machine to solicit an IP Header's total length field value within the echoed 'Port Unreachable" error message. This type of behavior is useful for building a signature-base of operating system responses, particularly when error messages contain other types of information that is useful identifying specific operating system responses.
CAPEC-332: ICMP IP 'ID' Field Error Message Probe
An adversary sends a UDP datagram having an assigned value to its internet identification field (ID) to a closed port on a target to observe the manner in which this bit is echoed back in the ICMP error message. This allows the attacker to construct a fingerprint of specific OS behaviors.
CAPEC-541: Application Fingerprinting
An adversary engages in fingerprinting activities to determine the type or version of an application installed on a remote target.
CAPEC-580: System Footprinting
An adversary engages in active probing and exploration activities to determine security information about a remote target system. Often times adversaries will rely on remote applications that can be probed for system configurations.