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.
323 vulnerabilities reference this CWE, most recent first.
GHSA-2FFW-H4MH-JJH5
Vulnerability from github – Published: 2025-11-18 15:30 – Updated: 2025-11-20 15:30Windu CMS is vulnerable to User Enumeration. This issue occurs during logon, where a difference in messages could allow an attacker to determine if the login is valid or not, enabling a brute force attack with valid logins.
The vendor was notified early about this vulnerability, but didn't respond with the details of vulnerability or vulnerable version range. Only version 4.1 was tested and confirmed as vulnerable, other versions were not tested and might also be vulnerable.
{
"affected": [],
"aliases": [
"CVE-2025-59116"
],
"database_specific": {
"cwe_ids": [
"CWE-204"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-11-18T15:16:34Z",
"severity": "MODERATE"
},
"details": "Windu CMS is vulnerable to User Enumeration. This issue occurs during logon, where a difference in messages could allow an attacker to determine if the login is valid or not, enabling a brute force attack with valid logins.\n\nThe vendor was notified early about this vulnerability, but didn\u0027t respond with the details of vulnerability or vulnerable version range. Only version 4.1 was tested and confirmed as vulnerable, other versions were not tested and might also be vulnerable.",
"id": "GHSA-2ffw-h4mh-jjh5",
"modified": "2025-11-20T15:30:20Z",
"published": "2025-11-18T15:30:56Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-59116"
},
{
"type": "WEB",
"url": "https://cert.pl/posts/2025/11/CVE-2025-59110"
},
{
"type": "WEB",
"url": "https://windu.org"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-2M7M-JHX5-8CRH
Vulnerability from github – Published: 2024-05-04 15:30 – Updated: 2024-05-04 15:30IBM Aspera Orchestrator 4.0.1 could allow a remote attacker to enumerate usernames due to observable response discrepancies. IBM X-Force ID: 248545.
{
"affected": [],
"aliases": [
"CVE-2023-27283"
],
"database_specific": {
"cwe_ids": [
"CWE-203",
"CWE-204"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-05-04T14:16:01Z",
"severity": "MODERATE"
},
"details": "IBM Aspera Orchestrator 4.0.1 could allow a remote attacker to enumerate usernames due to observable response discrepancies. IBM X-Force ID: 248545.",
"id": "GHSA-2m7m-jhx5-8crh",
"modified": "2024-05-04T15:30:31Z",
"published": "2024-05-04T15:30:31Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-27283"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/248545"
},
{
"type": "WEB",
"url": "https://www.ibm.com/support/pages/node/7150191"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-2PW7-5GJQ-98F6
Vulnerability from github – Published: 2025-10-23 18:31 – Updated: 2025-10-23 18:31Tibbo AggreGate Network Manager < 6.40.05 contains an observable response discrepancy in its login functionality. Authentication failure messages differ based on whether a supplied username exists or not, allowing an unauthenticated remote attacker to infer valid account identifiers. This can facilitate user enumeration and increase the likelihood of targeted brute-force or credential-stuffing attacks.
{
"affected": [],
"aliases": [
"CVE-2025-34155"
],
"database_specific": {
"cwe_ids": [
"CWE-204"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-10-23T17:15:36Z",
"severity": "MODERATE"
},
"details": "Tibbo AggreGate Network Manager \u003c 6.40.05 contains an observable response discrepancy in its login functionality. Authentication failure messages differ based on whether a supplied username exists or not, allowing an unauthenticated remote attacker to infer valid account identifiers. This can facilitate user enumeration and increase the likelihood of targeted brute-force or credential-stuffing attacks.",
"id": "GHSA-2pw7-5gjq-98f6",
"modified": "2025-10-23T18:31:15Z",
"published": "2025-10-23T18:31:15Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-34155"
},
{
"type": "WEB",
"url": "https://aggregate.digital/downloads.html"
},
{
"type": "WEB",
"url": "https://aggregate.digital/products/network-manager.html"
},
{
"type": "WEB",
"url": "https://www.vulncheck.com/advisories/tibbo-aggregate-network-manager-login-functionality-user-enumeration"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-2QW7-7PGW-GPC4
Vulnerability from github – Published: 2026-08-21 00:31 – Updated: 2026-08-21 00:31Observable response discrepancy in Azure Stack HCI allows an unauthorized attacker to disclose information over a network.
{
"affected": [],
"aliases": [
"CVE-2026-69519"
],
"database_specific": {
"cwe_ids": [
"CWE-204"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-20T22:18:00Z",
"severity": "HIGH"
},
"details": "Observable response discrepancy in Azure Stack HCI allows an unauthorized attacker to disclose information over a network.",
"id": "GHSA-2qw7-7pgw-gpc4",
"modified": "2026-08-21T00:31:22Z",
"published": "2026-08-21T00:31:22Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-69519"
},
{
"type": "WEB",
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69519"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-347X-877P-HCWX
Vulnerability from github – Published: 2020-05-13 22:19 – Updated: 2024-12-03 21:36In TYPO3 CMS 10.4.0 through 10.4.1, it has been discovered that time-based attacks can be used with the password reset functionality for backend users. This allows an attacker to mount user enumeration based on email addresses assigned to backend user accounts.
This has been fixed in 10.4.2.
References
- https://typo3.org/security/advisory/typo3-core-sa-2020-001
{
"affected": [
{
"package": {
"ecosystem": "Packagist",
"name": "typo3/cms-core"
},
"ranges": [
{
"events": [
{
"introduced": "10.0.0"
},
{
"fixed": "10.4.2"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Packagist",
"name": "typo3/cms"
},
"ranges": [
{
"events": [
{
"introduced": "10.0.0"
},
{
"fixed": "10.4.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2020-11063"
],
"database_specific": {
"cwe_ids": [
"CWE-203",
"CWE-204"
],
"github_reviewed": true,
"github_reviewed_at": "2020-05-13T22:16:54Z",
"nvd_published_at": "2020-05-13T23:15:11Z",
"severity": "LOW"
},
"details": "In TYPO3 CMS 10.4.0 through 10.4.1, it has been discovered that time-based attacks can be used with the password reset functionality for backend users. This allows an attacker to mount user enumeration based on email addresses assigned to backend user accounts.\n\nThis has been fixed in 10.4.2.\n\n### References\n* https://typo3.org/security/advisory/typo3-core-sa-2020-001",
"id": "GHSA-347x-877p-hcwx",
"modified": "2024-12-03T21:36:01Z",
"published": "2020-05-13T22:19:21Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/TYPO3/TYPO3.CMS/security/advisories/GHSA-347x-877p-hcwx"
},
{
"type": "WEB",
"url": "https://github.com/TYPO3/typo3/security/advisories/GHSA-347x-877p-hcwx"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2020-11063"
},
{
"type": "WEB",
"url": "https://github.com/TYPO3/typo3/commit/14929b98ecda0ce67329b0f25ca7c01ee85df574"
},
{
"type": "WEB",
"url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/typo3/cms-core/CVE-2020-11063.yaml"
},
{
"type": "WEB",
"url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/typo3/cms/CVE-2020-11063.yaml"
},
{
"type": "PACKAGE",
"url": "https://github.com/TYPO3/typo3"
},
{
"type": "WEB",
"url": "https://typo3.org/security/advisory/typo3-core-sa-2020-001"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "Information Disclosure in Password Reset"
}
GHSA-34X2-M38G-824F
Vulnerability from github – Published: 2026-03-13 21:31 – Updated: 2026-03-18 15:30Improper permission enforcement in Checkmk versions 2.4.0 before 2.4.0p23, 2.3.0 before 2.3.0p43, and 2.2.0 (EOL) allows authenticated users to enumerate existing hosts by observing different HTTP response codes in agent-receiver/register_existing endpoint, which could lead to information disclosure.
{
"affected": [],
"aliases": [
"CVE-2026-24097"
],
"database_specific": {
"cwe_ids": [
"CWE-204"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-13T19:54:16Z",
"severity": "MODERATE"
},
"details": "Improper permission enforcement in Checkmk versions 2.4.0 before 2.4.0p23, 2.3.0 before 2.3.0p43, and 2.2.0 (EOL) allows authenticated users to enumerate existing hosts by observing different HTTP response codes in agent-receiver/register_existing endpoint, which could lead to information disclosure.",
"id": "GHSA-34x2-m38g-824f",
"modified": "2026-03-18T15:30:42Z",
"published": "2026-03-13T21:31:46Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-24097"
},
{
"type": "WEB",
"url": "https://checkmk.com/werk/18993"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-36GF-GHCV-F3QQ
Vulnerability from github – Published: 2024-09-10 12:30 – Updated: 2024-09-10 12:30A vulnerability has been identified in Mendix Runtime V10 (All versions < V10.14.0 only if the basic authentication mechanism is used by the application), Mendix Runtime V10.12 (All versions < V10.12.2 only if the basic authentication mechanism is used by the application), Mendix Runtime V10.6 (All versions < V10.6.12 only if the basic authentication mechanism is used by the application), Mendix Runtime V8 (All versions only if the basic authentication mechanism is used by the application), Mendix Runtime V9 (All versions < V9.24.26 only if the basic authentication mechanism is used by the application). The authentication mechanism of affected applications contains an observable response discrepancy vulnerability when validating usernames. This could allow unauthenticated remote attackers to distinguish between valid and invalid usernames.
{
"affected": [],
"aliases": [
"CVE-2023-49069"
],
"database_specific": {
"cwe_ids": [
"CWE-204"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-09-10T10:15:08Z",
"severity": "MODERATE"
},
"details": "A vulnerability has been identified in Mendix Runtime V10 (All versions \u003c V10.14.0 only if the basic authentication mechanism is used by the application), Mendix Runtime V10.12 (All versions \u003c V10.12.2 only if the basic authentication mechanism is used by the application), Mendix Runtime V10.6 (All versions \u003c V10.6.12 only if the basic authentication mechanism is used by the application), Mendix Runtime V8 (All versions only if the basic authentication mechanism is used by the application), Mendix Runtime V9 (All versions \u003c V9.24.26 only if the basic authentication mechanism is used by the application). The authentication mechanism of affected applications contains an observable response discrepancy vulnerability when validating usernames. This could allow unauthenticated remote attackers to distinguish between valid and invalid usernames.",
"id": "GHSA-36gf-ghcv-f3qq",
"modified": "2024-09-10T12:30:37Z",
"published": "2024-09-10T12:30:37Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-49069"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-097435.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-36GX-9Q6H-G429
Vulnerability from github – Published: 2023-02-28 23:18 – Updated: 2026-05-29 20:49Impact
We are incorporating the password policies listed in https://github.com/vantage6/vantage6/issues/59. One measure is that we don't let the user know in case of wrong username/password combination if the username actually exists, to prevent that bots can guess usernames. However, if a wrong password is entered a number of times, the user account is blocked temporarily. This way you could still find out which usernames exist.
Patches
Update to 3.8.0+
Workarounds
No
References
https://github.com/vantage6/vantage6/issues/59
For more information
If you have any questions or comments about this advisory: * Email us at vantage6@iknl.nl
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "vantage6"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "3.8.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2022-39228"
],
"database_specific": {
"cwe_ids": [
"CWE-203",
"CWE-204"
],
"github_reviewed": true,
"github_reviewed_at": "2023-02-28T23:18:37Z",
"nvd_published_at": "2023-03-01T17:15:00Z",
"severity": "MODERATE"
},
"details": "### Impact\nWe are incorporating the password policies listed in https://github.com/vantage6/vantage6/issues/59. One measure is that we don\u0027t let the user know in case of wrong username/password combination if the username actually exists, to prevent that bots can guess usernames. However, if a wrong password is entered a number of times, the user account is blocked temporarily. This way you could still find out which usernames exist.\n\n### Patches\nUpdate to 3.8.0+\n\n### Workarounds\nNo\n\n### References\nhttps://github.com/vantage6/vantage6/issues/59\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Email us at [vantage6@iknl.nl](mailto:vantage6@iknl.nl)",
"id": "GHSA-36gx-9q6h-g429",
"modified": "2026-05-29T20:49:19Z",
"published": "2023-02-28T23:18:37Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/vantage6/vantage6/security/advisories/GHSA-36gx-9q6h-g429"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-39228"
},
{
"type": "WEB",
"url": "https://github.com/vantage6/vantage6/issues/59"
},
{
"type": "WEB",
"url": "https://github.com/vantage6/vantage6/pull/281"
},
{
"type": "WEB",
"url": "https://github.com/vantage6/vantage6/commit/ab4381c35d24add06f75d5a8a284321f7a340bd2"
},
{
"type": "WEB",
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/vantage6/PYSEC-2023-313.yaml"
},
{
"type": "WEB",
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/vantage6/PYSEC-2023-52.yaml"
},
{
"type": "PACKAGE",
"url": "https://github.com/vantage6/vantage6"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "vantage6 vulnerable to Observable Response Discrepancy"
}
GHSA-3765-5F6W-7P86
Vulnerability from github – Published: 2026-06-05 15:32 – Updated: 2026-06-05 15:32Observable response discrepancy vulnerability in HAVELSAN Inc. Geographic Tracking System allows System Footprinting.
This issue affects Geographic Tracking System: before v0.0.2.
{
"affected": [],
"aliases": [
"CVE-2026-6207"
],
"database_specific": {
"cwe_ids": [
"CWE-204"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-05T15:16:53Z",
"severity": "CRITICAL"
},
"details": "Observable response discrepancy vulnerability in HAVELSAN Inc. Geographic Tracking System allows System Footprinting.\n\nThis issue affects Geographic Tracking System: before v0.0.2.",
"id": "GHSA-3765-5f6w-7p86",
"modified": "2026-06-05T15:32:26Z",
"published": "2026-06-05T15:32:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-6207"
},
{
"type": "WEB",
"url": "https://siberguvenlik.gov.tr/guvenlik-bildirimleri/detay/tr-26-0325"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-387M-J3P9-3PHP
Vulnerability from github – Published: 2026-03-02 19:42 – Updated: 2026-03-02 19:42Summary
The password forgot endpoint returned different responses for registered and unregistered emails, allowing user enumeration.
Details
POST /api/v2/auth/password/forgot returned a success message for registered emails but 'Your email has not been registered.' for unknown emails. The fix returns a uniform response regardless of whether the email exists.
Impact
An unauthenticated attacker can determine whether an email is registered. No credentials or data are exposed.
Credit
This issue was reported by @Tulgaaaaaaaa.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.301.2"
},
"package": {
"ecosystem": "npm",
"name": "nocodb"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.301.3"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-28358"
],
"database_specific": {
"cwe_ids": [
"CWE-204"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-02T19:42:07Z",
"nvd_published_at": "2026-03-02T17:16:33Z",
"severity": "LOW"
},
"details": "### Summary\nThe password forgot endpoint returned different responses for registered and unregistered emails, allowing user enumeration.\n\n### Details\n`POST /api/v2/auth/password/forgot` returned a success message for registered emails but `\u0027Your email has not been registered.\u0027` for unknown emails. The fix returns a uniform response regardless of whether the email exists.\n\n### Impact\nAn unauthenticated attacker can determine whether an email is registered. No credentials or data are exposed.\n\n### Credit\nThis issue was reported by [@Tulgaaaaaaaa](https://github.com/Tulgaaaaaaaa).",
"id": "GHSA-387m-j3p9-3php",
"modified": "2026-03-02T19:42:07Z",
"published": "2026-03-02T19:42:07Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/nocodb/nocodb/security/advisories/GHSA-387m-j3p9-3php"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-28358"
},
{
"type": "PACKAGE",
"url": "https://github.com/nocodb/nocodb"
},
{
"type": "WEB",
"url": "https://github.com/nocodb/nocodb/releases/tag/0.301.3"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U",
"type": "CVSS_V4"
}
],
"summary": "NocoDB Vulnerable to User Enumeration via Password Reset Endpoint"
}
Mitigation MIT-46
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
- 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.