CWE-185
Incorrect Regular Expression
The product specifies a regular expression in a way that causes data to be improperly matched or compared.
CVE-2025-54365 (GCVE-0-2025-54365)
Vulnerability from cvelistv5
| Vendor | Product | Version | ||
|---|---|---|---|---|
| rennf93 | fastapi-guard |
Version: >= 3.0.1, < 3.0.2 |
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"id": "CVE-2025-54365",
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"timestamp": "2025-07-24T13:13:00.507260Z",
"version": "2.0.3"
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"url": "https://github.com/rennf93/fastapi-guard/security/advisories/GHSA-rrf6-pxg8-684g"
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"title": "CISA ADP Vulnrichment"
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"product": "fastapi-guard",
"vendor": "rennf93",
"versions": [
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"status": "affected",
"version": "\u003e= 3.0.1, \u003c 3.0.2"
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"lang": "en",
"value": "fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect penetration attempts and more. In version 3.0.1, the regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit. This type of patch fails to detect cases in which the string representing the attributes of a \u003cscript\u003e tag exceeds 100 characters. As a result, most of the regex patterns present in version 3.0.1 can be bypassed. This is fixed in version 3.0.2."
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"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
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"subConfidentialityImpact": "NONE",
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"userInteraction": "NONE",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P",
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"description": "CWE-185: Incorrect Regular Expression",
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"providerMetadata": {
"dateUpdated": "2025-07-23T22:11:36.441Z",
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"url": "https://github.com/rennf93/fastapi-guard/security/advisories/GHSA-rrf6-pxg8-684g"
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"advisory": "GHSA-rrf6-pxg8-684g",
"discovery": "UNKNOWN"
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"title": "fastapi-guard patch contains bypassable RegEx"
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"datePublished": "2025-07-23T22:11:36.441Z",
"dateReserved": "2025-07-21T16:12:20.731Z",
"dateUpdated": "2025-07-24T13:36:52.638Z",
"state": "PUBLISHED"
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Mitigation ID: MIT-45
Phase: Architecture and Design
Strategy: Refactoring
Description:
- Regular expressions can become error prone when defining a complex language even for those experienced in writing grammars. Determine if several smaller regular expressions simplify one large regular expression. Also, subject the regular expression to thorough testing techniques such as equivalence partitioning, boundary value analysis, and robustness. After testing and a reasonable confidence level is achieved, a regular expression may not be foolproof. If an exploit is allowed to slip through, then record the exploit and refactor the regular expression.
CAPEC-15: Command Delimiters
An attack of this type exploits a programs' vulnerabilities that allows an attacker's commands to be concatenated onto a legitimate command with the intent of targeting other resources such as the file system or database. The system that uses a filter or denylist input validation, as opposed to allowlist validation is vulnerable to an attacker who predicts delimiters (or combinations of delimiters) not present in the filter or denylist. As with other injection attacks, the attacker uses the command delimiter payload as an entry point to tunnel through the application and activate additional attacks through SQL queries, shell commands, network scanning, and so on.
CAPEC-6: Argument Injection
An attacker changes the behavior or state of a targeted application through injecting data or command syntax through the targets use of non-validated and non-filtered arguments of exposed services or methods.
CAPEC-79: Using Slashes in Alternate Encoding
This attack targets the encoding of the Slash characters. An adversary would try to exploit common filtering problems related to the use of the slashes characters to gain access to resources on the target host. Directory-driven systems, such as file systems and databases, typically use the slash character to indicate traversal between directories or other container components. For murky historical reasons, PCs (and, as a result, Microsoft OSs) choose to use a backslash, whereas the UNIX world typically makes use of the forward slash. The schizophrenic result is that many MS-based systems are required to understand both forms of the slash. This gives the adversary many opportunities to discover and abuse a number of common filtering problems. The goal of this pattern is to discover server software that only applies filters to one version, but not the other.