CWE · MITRE source
CWE-551Incorrect Behavior Order: Authorization Before Parsing and Canonicalization
If a web server does not fully parse requested URLs before it examines them for authorization, it may be possible for an attacker to bypass authorization protection.
For instance, the character strings /./ and / both mean current directory. If /SomeDirectory is a protected directory and an attacker requests /./SomeDirectory, the attacker may be able to gain access to the resource if /./ is not converted to / before the authorization check is performed.
Last updated: 09 May 2026 03:25 UTC
NIST 800-53 r5 controls that address this weakness (0)AI
| Control | Title | Family | Why it addresses this CWE |
|---|---|---|---|
| No NIST controls proposed yet. | |||
Top CVEs of this weakness type, ranked by Risk Priority
| CVE | Risk | CVSS | EPSS | Published |
|---|---|---|---|---|
CVE-2021-28164 | 6.7 | 5.3 | 0.9348 | 2021-04-01 |
CVE-2021-34429 | 6.7 | 5.3 | 0.9378 | 2021-07-15 |
CVE-2023-23924 | 5.1 | 10.0 | 0.5146 | 2023-02-01 |
CVE-2021-28165 | 2.2 | 7.5 | 0.1199 | 2021-04-01 |
CVE-2016-20030 | 2.0 | 9.8 | 0.0004 | 2026-03-16 |
CVE-2021-32777 | 1.7 | 8.6 | 0.0002 | 2021-08-24 |
CVE-2021-32779 | 1.7 | 8.6 | 0.0003 | 2021-08-24 |
CVE-2026-4636 | 1.6 | 8.1 | 0.0003 | 2026-04-02 |
CVE-2021-31384 | 1.5 | 7.2 | 0.0037 | 2021-10-19 |
CVE-2026-0707 | 1.1 | 5.3 | 0.0003 | 2026-01-08 |