CWE-172
Allowed-with-ReviewEncoding Error
Abstraction: Class · Status: Draft
The product does not properly encode or decode the data, resulting in unexpected values.
27 vulnerabilities reference this CWE, most recent first.
GHSA-F7P3-3696-M8FM
Vulnerability from github – Published: 2022-05-17 03:42 – Updated: 2022-05-17 03:42codecs/hevcdec/SoftHEVC.cpp in libstagefright in mediaserver in Android 6.0.1 before 2016-08-01 mishandles decoder errors, which allows remote attackers to cause a denial of service (device hang or reboot) via a crafted media file, aka internal bug 28816956.
{
"affected": [],
"aliases": [
"CVE-2016-3827"
],
"database_specific": {
"cwe_ids": [
"CWE-172"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2016-08-05T20:59:00Z",
"severity": "HIGH"
},
"details": "codecs/hevcdec/SoftHEVC.cpp in libstagefright in mediaserver in Android 6.0.1 before 2016-08-01 mishandles decoder errors, which allows remote attackers to cause a denial of service (device hang or reboot) via a crafted media file, aka internal bug 28816956.",
"id": "GHSA-f7p3-3696-m8fm",
"modified": "2022-05-17T03:42:16Z",
"published": "2022-05-17T03:42:16Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2016-3827"
},
{
"type": "WEB",
"url": "https://android.googlesource.com/platform/frameworks/av/+/a4567c66f4764442c6cb7b5c1858810194480fb5"
},
{
"type": "WEB",
"url": "http://source.android.com/security/bulletin/2016-08-01.html"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/92221"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-H5X3-XFC9-M39H
Vulnerability from github – Published: 2026-06-15 17:33 – Updated: 2026-06-15 17:33Description
Symfony\Component\Routing\Generator\UrlGenerator::doGenerate() percent-encodes . and .. path segments so that the generated URL still resolves to the originating route after RFC 3986 §5.2.4 dot-segment removal (which strict RFC-3986 consumers — routers, reverse proxies, HTTP clients — perform before percent-decoding).
The encoding was implemented as strtr($url, ['/../' => '/%2E%2E/', '/./' => '/%2E/']) plus a trailing-segment fixup. strtr advances past the trailing / of each match, so the next dot-segment in a chained sequence was left unescaped:
| Input | Output (before fix) | Expected |
|---|---|---|
/../../../ |
/%2E%2E/../%2E%2E/ |
/%2E%2E/%2E%2E/%2E%2E/ |
/foo/../../../bar |
/foo/%2E%2E/../%2E%2E/bar |
/foo/%2E%2E/%2E%2E/%2E%2E/bar |
When a route exposes a parameter constrained by a permissive requirement (.+, .*, or similar) that accepts dots and slashes, attacker-controlled chained .. or . segments produce a generated URL that, under strict RFC 3986 normalization, collapses to a different path than the originating route. The Twig path() / url() helpers and any server-side use of UrlGenerator are affected. Same class of route round-trip integrity issue as CVE-2026-45065.
Note: WHATWG-conformant browsers treat %2E/%2E%2E as dot-segments during URL parsing, so the encoding never protected browser-side traversal. The defense exists for RFC-3986-conformant consumers; restoring it for chained segments closes the gap there.
Resolution
UrlGenerator now matches every /. or /.. dot-segment in a single left-to-right preg_replace_callback pass using a lookahead that does not consume the trailing /, so adjacent dot-segments are encoded correctly.
The patches for this issue are available here for branch 5.4 (and forward-ported to 6.4, 7.4, 8.0 and 8.1).
Credits
Symfony would like to thank Alex Pott for reporting the issue and Nicolas Grekas for providing the fix.
{
"affected": [
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/routing"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "5.4.53"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/routing"
},
"ranges": [
{
"events": [
{
"introduced": "6.0.0"
},
{
"fixed": "6.4.41"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/routing"
},
"ranges": [
{
"events": [
{
"introduced": "7.0.0"
},
{
"fixed": "7.4.13"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/routing"
},
"ranges": [
{
"events": [
{
"introduced": "8.0.0"
},
{
"fixed": "8.0.13"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/symfony"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "5.4.53"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/symfony"
},
"ranges": [
{
"events": [
{
"introduced": "6.0.0"
},
{
"fixed": "6.4.41"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/symfony"
},
"ranges": [
{
"events": [
{
"introduced": "7.0.0"
},
{
"fixed": "7.4.13"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Packagist",
"name": "symfony/symfony"
},
"ranges": [
{
"events": [
{
"introduced": "8.0.0"
},
{
"fixed": "8.0.13"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-48784"
],
"database_specific": {
"cwe_ids": [
"CWE-172",
"CWE-601"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-15T17:33:46Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "### Description\n\n`Symfony\\Component\\Routing\\Generator\\UrlGenerator::doGenerate()` percent-encodes `.` and `..` path segments so that the generated URL still resolves to the originating route after RFC 3986 \u00a75.2.4 dot-segment removal (which strict RFC-3986 consumers \u2014 routers, reverse proxies, HTTP clients \u2014 perform *before* percent-decoding).\n\nThe encoding was implemented as `strtr($url, [\u0027/../\u0027 =\u003e \u0027/%2E%2E/\u0027, \u0027/./\u0027 =\u003e \u0027/%2E/\u0027])` plus a trailing-segment fixup. `strtr` advances past the trailing `/` of each match, so the next dot-segment in a chained sequence was left unescaped:\n\n| Input | Output (before fix) | Expected |\n| -------------------- | ---------------------------------------- | ----------------------------------- |\n| `/../../../` | `/%2E%2E/../%2E%2E/` | `/%2E%2E/%2E%2E/%2E%2E/` |\n| `/foo/../../../bar` | `/foo/%2E%2E/../%2E%2E/bar` | `/foo/%2E%2E/%2E%2E/%2E%2E/bar` |\n\nWhen a route exposes a parameter constrained by a permissive requirement (`.+`, `.*`, or similar) that accepts dots and slashes, attacker-controlled chained `..` or `.` segments produce a generated URL that, under strict RFC 3986 normalization, collapses to a different path than the originating route. The Twig `path()` / `url()` helpers and any server-side use of `UrlGenerator` are affected. Same class of route round-trip integrity issue as CVE-2026-45065.\n\nNote: WHATWG-conformant browsers treat `%2E`/`%2E%2E` as dot-segments during URL parsing, so the encoding never protected browser-side traversal. The defense exists for RFC-3986-conformant consumers; restoring it for chained segments closes the gap there.\n\n### Resolution\n\n`UrlGenerator` now matches every `/.` or `/..` dot-segment in a single left-to-right `preg_replace_callback` pass using a lookahead that does not consume the trailing `/`, so adjacent dot-segments are encoded correctly.\n\nThe patches for this issue are available [here](https://github.com/symfony/symfony/commit/4b63c3a3f7af04ecd79c89a594b0b02a01990b1d) for branch 5.4 (and forward-ported to 6.4, 7.4, 8.0 and 8.1).\n\n### Credits\n\nSymfony would like to thank Alex Pott for reporting the issue and Nicolas Grekas for providing the fix.",
"id": "GHSA-h5x3-xfc9-m39h",
"modified": "2026-06-15T17:33:46Z",
"published": "2026-06-15T17:33:46Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/symfony/symfony/security/advisories/GHSA-h5x3-xfc9-m39h"
},
{
"type": "WEB",
"url": "https://github.com/symfony/symfony/commit/4b63c3a3f7af04ecd79c89a594b0b02a01990b1d"
},
{
"type": "WEB",
"url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/routing/CVE-2026-48784.yaml"
},
{
"type": "WEB",
"url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-48784.yaml"
},
{
"type": "PACKAGE",
"url": "https://github.com/symfony/symfony"
},
{
"type": "WEB",
"url": "https://symfony.com/cve-2026-48784"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Symfony: UrlGenerator Dot-Segment Encoding Skips Every Other Chained `../` or `./` \u2192 Generated URL Collapses Off-Route Under RFC 3986 Normalization"
}
GHSA-JH85-MGR3-8F33
Vulnerability from github – Published: 2025-09-26 18:31 – Updated: 2025-09-26 21:30Squid through 7.1 mishandles ASN.1 encoding of long SNMP OIDs. This occurs in asn_build_objid in lib/snmplib/asn1.c.
{
"affected": [],
"aliases": [
"CVE-2025-59362"
],
"database_specific": {
"cwe_ids": [
"CWE-121",
"CWE-172"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-09-26T16:15:48Z",
"severity": "HIGH"
},
"details": "Squid through 7.1 mishandles ASN.1 encoding of long SNMP OIDs. This occurs in asn_build_objid in lib/snmplib/asn1.c.",
"id": "GHSA-jh85-mgr3-8f33",
"modified": "2025-09-26T21:30:29Z",
"published": "2025-09-26T18:31:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-59362"
},
{
"type": "WEB",
"url": "https://github.com/squid-cache/squid/pull/2149"
},
{
"type": "WEB",
"url": "https://github.com/Microsvuln/advisories/blob/main/CVE-2025-59362/CVE-2025-59362.md"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-V43F-895R-CHHH
Vulnerability from github – Published: 2026-05-13 18:30 – Updated: 2026-05-13 18:30When NGINX Open Source is configured to proxy HTTP/2 traffic by setting proxy_http_version to 2, and also uses proxy_set_body, an attacker may be able to inject frame headers and payload bytes to the upstream peer. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
{
"affected": [],
"aliases": [
"CVE-2026-42926"
],
"database_specific": {
"cwe_ids": [
"CWE-172"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-13T16:16:49Z",
"severity": "MODERATE"
},
"details": "When NGINX Open Source is configured to proxy HTTP/2 traffic by setting proxy_http_version\u00a0to 2, and also uses proxy_set_body, an attacker may be able to inject frame headers and payload bytes to the upstream peer.\u00a0 Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.",
"id": "GHSA-v43f-895r-chhh",
"modified": "2026-05-13T18:30:56Z",
"published": "2026-05-13T18:30:56Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42926"
},
{
"type": "WEB",
"url": "https://my.f5.com/manage/s/article/K000161131"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/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-VGHF-HV5Q-VC2G
Vulnerability from github – Published: 2025-11-27 06:31 – Updated: 2026-01-31 03:33Versions of the package validator before 13.15.22 are vulnerable to Incomplete Filtering of One or More Instances of Special Elements in the isLength() function that does not take into account Unicode variation selectors (\uFE0F, \uFE0E) appearing in a sequence which lead to improper string length calculation. This can lead to an application using isLength for input validation accepting strings significantly longer than intended, resulting in issues like data truncation in databases, buffer overflows in other system components, or denial-of-service.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "validator"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "13.15.22"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2025-12758"
],
"database_specific": {
"cwe_ids": [
"CWE-172",
"CWE-792"
],
"github_reviewed": true,
"github_reviewed_at": "2025-12-02T16:51:42Z",
"nvd_published_at": "2025-11-27T05:16:12Z",
"severity": "HIGH"
},
"details": "Versions of the package validator before 13.15.22 are vulnerable to Incomplete Filtering of One or More Instances of Special Elements in the isLength() function that does not take into account Unicode variation selectors (\\uFE0F, \\uFE0E) appearing in a sequence which lead to improper string length calculation. This can lead to an application using isLength for input validation accepting strings significantly longer than intended, resulting in issues like data truncation in databases, buffer overflows in other system components, or denial-of-service.",
"id": "GHSA-vghf-hv5q-vc2g",
"modified": "2026-01-31T03:33:13Z",
"published": "2025-11-27T06:31:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-12758"
},
{
"type": "WEB",
"url": "https://github.com/validatorjs/validator.js/pull/2616"
},
{
"type": "WEB",
"url": "https://github.com/validatorjs/validator.js/commit/d457ecaf55b0f3d8bd379d82757425d0d13dd382"
},
{
"type": "WEB",
"url": "https://gist.github.com/koral--/ad31208b25b9e3d1e2e35f1d4d72572e"
},
{
"type": "PACKAGE",
"url": "https://github.com/validatorjs/validator.js"
},
{
"type": "WEB",
"url": "https://security.snyk.io/vuln/SNYK-JS-VALIDATOR-13653476"
},
{
"type": "WEB",
"url": "http://seclists.org/fulldisclosure/2026/Jan/27"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/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"
}
],
"summary": "Validator is Vulnerable to Incomplete Filtering of One or More Instances of Special Elements"
}
GHSA-WQXC-QRQ4-W5V4
Vulnerability from github – Published: 2021-08-25 21:01 – Updated: 2022-06-15 19:41An issue was discovered in the abi_stable crate before 0.9.1 for Rust. A retain call can create an invalid UTF-8 string, violating soundness.
{
"affected": [
{
"package": {
"ecosystem": "crates.io",
"name": "abi_stable"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.9.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2020-36213"
],
"database_specific": {
"cwe_ids": [
"CWE-172"
],
"github_reviewed": true,
"github_reviewed_at": "2021-07-26T17:18:54Z",
"nvd_published_at": "2021-01-26T18:15:00Z",
"severity": "HIGH"
},
"details": "An issue was discovered in the abi_stable crate before 0.9.1 for Rust. A retain call can create an invalid UTF-8 string, violating soundness.",
"id": "GHSA-wqxc-qrq4-w5v4",
"modified": "2022-06-15T19:41:46Z",
"published": "2021-08-25T21:01:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2020-36213"
},
{
"type": "WEB",
"url": "https://github.com/rodrimati1992/abi_stable_crates/issues/44"
},
{
"type": "WEB",
"url": "https://rustsec.org/advisories/RUSTSEC-2020-0105.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "Update unsound DrainFilter and RString::retain"
}
GHSA-WVVV-6XF9-8F8R
Vulnerability from github – Published: 2022-05-24 16:57 – Updated: 2022-05-26 00:01A vulnerability in the Secure Sockets Layer (SSL) VPN feature of Cisco Adaptive Security Appliance (ASA) Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition that prevents the creation of new SSL/Transport Layer Security (TLS) connections to an affected device. The vulnerability is due to incorrect handling of Base64-encoded strings. An attacker could exploit this vulnerability by opening many SSL VPN sessions to an affected device. The attacker would need to have valid user credentials on the affected device to exploit this vulnerability. A successful exploit could allow the attacker to overwrite a special system memory location, which will eventually result in memory allocation errors for new SSL/TLS sessions to the device, preventing successful establishment of these sessions. A reload of the device is required to recover from this condition. Established SSL/TLS connections to the device and SSL/TLS connections through the device are not affected. Note: Although this vulnerability is in the SSL VPN feature, successful exploitation of this vulnerability would affect all new SSL/TLS sessions to the device, including management sessions.
{
"affected": [],
"aliases": [
"CVE-2019-12677"
],
"database_specific": {
"cwe_ids": [
"CWE-172",
"CWE-755"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2019-10-02T19:15:00Z",
"severity": "MODERATE"
},
"details": "A vulnerability in the Secure Sockets Layer (SSL) VPN feature of Cisco Adaptive Security Appliance (ASA) Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition that prevents the creation of new SSL/Transport Layer Security (TLS) connections to an affected device. The vulnerability is due to incorrect handling of Base64-encoded strings. An attacker could exploit this vulnerability by opening many SSL VPN sessions to an affected device. The attacker would need to have valid user credentials on the affected device to exploit this vulnerability. A successful exploit could allow the attacker to overwrite a special system memory location, which will eventually result in memory allocation errors for new SSL/TLS sessions to the device, preventing successful establishment of these sessions. A reload of the device is required to recover from this condition. Established SSL/TLS connections to the device and SSL/TLS connections through the device are not affected. Note: Although this vulnerability is in the SSL VPN feature, successful exploitation of this vulnerability would affect all new SSL/TLS sessions to the device, including management sessions.",
"id": "GHSA-wvvv-6xf9-8f8r",
"modified": "2022-05-26T00:01:16Z",
"published": "2022-05-24T16:57:35Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-12677"
},
{
"type": "WEB",
"url": "https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20191002-asa-ssl-vpn-dos"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
Mitigation MIT-5
Strategy: Input Validation
- Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Mitigation MIT-28
Strategy: Output Encoding
While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (CWE-88).
Mitigation MIT-20
Strategy: Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
CAPEC-120: Double Encoding
The adversary utilizes a repeating of the encoding process for a set of characters (that is, character encoding a character encoding of a character) to obfuscate the payload of a particular request. This may allow the adversary to bypass filters that attempt to detect illegal characters or strings, such as those that might be used in traversal or injection attacks. Filters may be able to catch illegal encoded strings, but may not catch doubly encoded strings. For example, a dot (.), often used in path traversal attacks and therefore often blocked by filters, could be URL encoded as %2E. However, many filters recognize this encoding and would still block the request. In a double encoding, the % in the above URL encoding would be encoded again as %25, resulting in %252E which some filters might not catch, but which could still be interpreted as a dot (.) by interpreters on the target.
CAPEC-267: Leverage Alternate Encoding
An adversary leverages the possibility to encode potentially harmful input or content used by applications such that the applications are ineffective at validating this encoding standard.
CAPEC-3: Using Leading 'Ghost' Character Sequences to Bypass Input Filters
Some APIs will strip certain leading characters from a string of parameters. An adversary can intentionally introduce leading "ghost" characters (extra characters that don't affect the validity of the request at the API layer) that enable the input to pass the filters and therefore process the adversary's input. This occurs when the targeted API will accept input data in several syntactic forms and interpret it in the equivalent semantic way, while the filter does not take into account the full spectrum of the syntactic forms acceptable to the targeted API.
CAPEC-52: Embedding NULL Bytes
An adversary embeds one or more null bytes in input to the target software. This attack relies on the usage of a null-valued byte as a string terminator in many environments. The goal is for certain components of the target software to stop processing the input when it encounters the null byte(s).
CAPEC-53: Postfix, Null Terminate, and Backslash
If a string is passed through a filter of some kind, then a terminal NULL may not be valid. Using alternate representation of NULL allows an adversary to embed the NULL mid-string while postfixing the proper data so that the filter is avoided. One example is a filter that looks for a trailing slash character. If a string insertion is possible, but the slash must exist, an alternate encoding of NULL in mid-string may be used.
CAPEC-64: Using Slashes and URL Encoding Combined to Bypass Validation Logic
This attack targets the encoding of the URL combined with the encoding of the slash characters. An attacker can take advantage of the multiple ways of encoding a URL and abuse the interpretation of the URL. A URL may contain special character that need special syntax handling in order to be interpreted. Special characters are represented using a percentage character followed by two digits representing the octet code of the original character (%HEX-CODE). For instance US-ASCII space character would be represented with %20. This is often referred as escaped ending or percent-encoding. Since the server decodes the URL from the requests, it may restrict the access to some URL paths by validating and filtering out the URL requests it received. An attacker will try to craft an URL with a sequence of special characters which once interpreted by the server will be equivalent to a forbidden URL. It can be difficult to protect against this attack since the URL can contain other format of encoding such as UTF-8 encoding, Unicode-encoding, etc.
CAPEC-71: Using Unicode Encoding to Bypass Validation Logic
An attacker may provide a Unicode string to a system component that is not Unicode aware and use that to circumvent the filter or cause the classifying mechanism to fail to properly understanding the request. That may allow the attacker to slip malicious data past the content filter and/or possibly cause the application to route the request incorrectly.
CAPEC-72: URL Encoding
This attack targets the encoding of the URL. An adversary can take advantage of the multiple way of encoding an URL and abuse the interpretation of the URL.
CAPEC-78: Using Escaped Slashes in Alternate Encoding
This attack targets the use of the backslash in alternate encoding. An adversary can provide a backslash as a leading character and causes a parser to believe that the next character is special. This is called an escape. By using that trick, the adversary tries to exploit alternate ways to encode the same character which leads to filter problems and opens avenues to attack.
CAPEC-80: Using UTF-8 Encoding to Bypass Validation Logic
This attack is a specific variation on leveraging alternate encodings to bypass validation logic. This attack leverages the possibility to encode potentially harmful input in UTF-8 and submit it to applications not expecting or effective at validating this encoding standard making input filtering difficult. UTF-8 (8-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode. Legal UTF-8 characters are one to four bytes long. However, early version of the UTF-8 specification got some entries wrong (in some cases it permitted overlong characters). UTF-8 encoders are supposed to use the "shortest possible" encoding, but naive decoders may accept encodings that are longer than necessary. According to the RFC 3629, a particularly subtle form of this attack can be carried out against a parser which performs security-critical validity checks against the UTF-8 encoded form of its input, but interprets certain illegal octet sequences as characters.