CWE-22
Allowed-with-ReviewImproper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Abstraction: Base · Status: Stable
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
13064 vulnerabilities reference this CWE, most recent first.
GHSA-VM2H-2QJ9-R6XV
Vulnerability from github – Published: 2022-05-24 16:54 – Updated: 2024-04-04 01:46Cuberite before 2019-06-11 allows webadmin directory traversal via ....// because the protection mechanism simply removes one ../ substring.
{
"affected": [],
"aliases": [
"CVE-2019-15516"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2019-08-23T15:15:00Z",
"severity": "HIGH"
},
"details": "Cuberite before 2019-06-11 allows webadmin directory traversal via ....// because the protection mechanism simply removes one ../ substring.",
"id": "GHSA-vm2h-2qj9-r6xv",
"modified": "2024-04-04T01:46:59Z",
"published": "2022-05-24T16:54:40Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-15516"
},
{
"type": "WEB",
"url": "https://github.com/cuberite/cuberite/pull/4341"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-VM37-PW86-PCC9
Vulnerability from github – Published: 2022-05-17 03:01 – Updated: 2022-05-17 03:01IBM Kenexa LMS on Cloud 13.1 and 13.2 - 13.2.4 could allow a remote attacker to traverse directories on the system. An attacker could send a specially-crafted URL request containing "dot dot" sequences (/../) to view arbitrary files on the system.
{
"affected": [],
"aliases": [
"CVE-2016-8913"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2017-02-01T20:59:00Z",
"severity": "MODERATE"
},
"details": "IBM Kenexa LMS on Cloud 13.1 and 13.2 - 13.2.4 could allow a remote attacker to traverse directories on the system. An attacker could send a specially-crafted URL request containing \"dot dot\" sequences (/../) to view arbitrary files on the system.",
"id": "GHSA-vm37-pw86-pcc9",
"modified": "2022-05-17T03:01:32Z",
"published": "2022-05-17T03:01:32Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2016-8913"
},
{
"type": "WEB",
"url": "http://www.ibm.com/support/docview.wss?uid=swg21993982"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/94304"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-VM3J-FRHC-9M3C
Vulnerability from github – Published: 2022-05-17 00:41 – Updated: 2022-05-17 00:41Directory traversal vulnerability in index.php in MyPHPSite, when magic_quotes_gpc is disabled, allows remote attackers to read arbitrary files via a .. (dot dot) in the mod parameter.
{
"affected": [],
"aliases": [
"CVE-2008-6018"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2009-02-02T22:00:00Z",
"severity": "MODERATE"
},
"details": "Directory traversal vulnerability in index.php in MyPHPSite, when magic_quotes_gpc is disabled, allows remote attackers to read arbitrary files via a .. (dot dot) in the mod parameter.",
"id": "GHSA-vm3j-frhc-9m3c",
"modified": "2022-05-17T00:41:39Z",
"published": "2022-05-17T00:41:39Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2008-6018"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/7519"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/33171"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/32919"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-VM3M-GQC9-52CH
Vulnerability from github – Published: 2022-07-12 00:00 – Updated: 2022-07-16 00:00The Wildog/flask-file-server repository through 2020-02-20 on GitHub allows absolute path traversal because the Flask send_file function is used unsafely.
{
"affected": [],
"aliases": [
"CVE-2022-31527"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2022-07-11T01:15:00Z",
"severity": "CRITICAL"
},
"details": "The Wildog/flask-file-server repository through 2020-02-20 on GitHub allows absolute path traversal because the Flask send_file function is used unsafely.",
"id": "GHSA-vm3m-gqc9-52ch",
"modified": "2022-07-16T00:00:33Z",
"published": "2022-07-12T00:00:57Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-31527"
},
{
"type": "WEB",
"url": "https://github.com/github/securitylab/issues/669#issuecomment-1117265726"
}
],
"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:L",
"type": "CVSS_V3"
}
]
}
GHSA-VM56-HJ47-795X
Vulnerability from github – Published: 2022-05-24 17:41 – Updated: 2022-05-24 17:41autoar-extractor.c in GNOME gnome-autoar through 0.2.4, as used by GNOME Shell, Nautilus, and other software, allows Directory Traversal during extraction because it lacks a check of whether a file's parent is a symlink to a directory outside of the intended extraction location.
{
"affected": [],
"aliases": [
"CVE-2020-36241"
],
"database_specific": {
"cwe_ids": [
"CWE-22",
"CWE-59"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2021-02-05T14:15:00Z",
"severity": "MODERATE"
},
"details": "autoar-extractor.c in GNOME gnome-autoar through 0.2.4, as used by GNOME Shell, Nautilus, and other software, allows Directory Traversal during extraction because it lacks a check of whether a file\u0027s parent is a symlink to a directory outside of the intended extraction location.",
"id": "GHSA-vm56-hj47-795x",
"modified": "2022-05-24T17:41:11Z",
"published": "2022-05-24T17:41:11Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2020-36241"
},
{
"type": "WEB",
"url": "https://gitlab.gnome.org/GNOME/gnome-autoar/-/commit/adb067e645732fdbe7103516e506d09eb6a54429"
},
{
"type": "WEB",
"url": "https://gitlab.gnome.org/GNOME/gnome-autoar/-/issues/7"
},
{
"type": "WEB",
"url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BN5TVQ7OHZEGY6AGFLAZWCVCI53RYNHQ"
},
{
"type": "WEB",
"url": "https://security.gentoo.org/glsa/202105-10"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-VM5M-R8F6-QW49
Vulnerability from github – Published: 2022-05-14 01:28 – Updated: 2022-05-14 01:28PHP Scripts Mall Medical Store Script 3.0.3 allows Path Traversal by navigating to the parent directory of a jpg or png file.
{
"affected": [],
"aliases": [
"CVE-2019-9607"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2019-03-06T22:29:00Z",
"severity": "MODERATE"
},
"details": "PHP Scripts Mall Medical Store Script 3.0.3 allows Path Traversal by navigating to the parent directory of a jpg or png file.",
"id": "GHSA-vm5m-r8f6-qw49",
"modified": "2022-05-14T01:28:06Z",
"published": "2022-05-14T01:28:06Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-9607"
},
{
"type": "WEB",
"url": "https://hackingvila.wordpress.com/2019/02/24/php-scripts-mall-medical-store-script-3-0-3-has-path-traversal"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-VM68-XCC6-2F3G
Vulnerability from github – Published: 2022-05-13 01:32 – Updated: 2022-05-13 01:32IBM WebSphere Application Server 7.0, 8.0, 8.5, and 9.0 using Enterprise bundle Archives (EBA) could allow a local attacker to traverse directories on the system. By persuading a victim to extract a specially-crafted ZIP archive containing "dot dot slash" sequences (../), an attacker could exploit this vulnerability to write to arbitrary files on the system. Note: This vulnerability is known as "Zip-Slip". IBM X-Force ID: 149427.
{
"affected": [],
"aliases": [
"CVE-2018-1797"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2018-11-16T15:29:00Z",
"severity": "MODERATE"
},
"details": "IBM WebSphere Application Server 7.0, 8.0, 8.5, and 9.0 using Enterprise bundle Archives (EBA) could allow a local attacker to traverse directories on the system. By persuading a victim to extract a specially-crafted ZIP archive containing \"dot dot slash\" sequences (../), an attacker could exploit this vulnerability to write to arbitrary files on the system. Note: This vulnerability is known as \"Zip-Slip\". IBM X-Force ID: 149427.",
"id": "GHSA-vm68-xcc6-2f3g",
"modified": "2022-05-13T01:32:38Z",
"published": "2022-05-13T01:32:38Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2018-1797"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/149427"
},
{
"type": "WEB",
"url": "https://www.ibm.com/support/docview.wss?uid=ibm10730699"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/105982"
},
{
"type": "WEB",
"url": "http://www.securitytracker.com/id/1042146"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-VM69-H85X-8P85
Vulnerability from github – Published: 2026-03-18 20:10 – Updated: 2026-03-25 18:12Summary
The IsSensitivePath() function in kernel/util/path.go uses a denylist approach that was recently expanded (GHSA-h5vh-m7fg-w5h6, commit 9914fd1) but remains incomplete. Multiple security-relevant Linux directories are not blocked, including /opt (application data), /usr (local configs/binaries), /home (other users), /mnt and /media (mounted volumes). The globalCopyFiles and importStdMd endpoints rely on IsSensitivePath as their primary defense against reading files outside the workspace.
Details
Current denylist in kernel/util/path.go:391-405:
prefixes := []string{
"/.", // dotfiles
"/etc", // system config
"/root", // root home
"/var", // variable data
"/proc", // process info
"/sys", // sysfs
"/run", // runtime data
"/bin", // binaries
"/boot", // boot files
"/dev", // devices
"/lib", // libraries
"/srv", // service data
"/tmp", // temp files
}
NOT blocked:
- /opt — commonly contains application data, databases, credentials. In SiYuan Docker, /opt/siyuan/ contains the application itself.
- /usr — contains /usr/local/etc, /usr/local/share, custom configs
- /home — other users' home directories (only ~/.ssh and ~/.config of the current HomeDir are blocked via separate checks, but other users' homes are accessible)
- /mnt, /media — mounted volumes, network shares, often containing secrets
- /snap — snap package data
- /sbin, /lib64 — system binaries/libraries
The globalCopyFiles endpoint at kernel/api/file.go:82 uses IsSensitivePath as its sole path validation:
if util.IsSensitivePath(absSrc) {
// reject
continue
}
// File is copied into workspace — then readable via /api/file/getFile
PoC
# Read SiYuan's own application files from /opt (Docker deployment)
curl -s 'http://127.0.0.1:6806/api/file/globalCopyFiles' \
-H 'Authorization: Token YOUR_API_TOKEN' \
-H 'Content-Type: application/json' \
-d '{"srcs":["/opt/siyuan/kernel/SiYuan-Kernel"],"destDir":"data/assets"}'
# Then read the copied file from workspace
curl -s 'http://127.0.0.1:6806/api/file/getFile' \
-H 'Authorization: Token YOUR_API_TOKEN' \
-H 'Content-Type: application/json' \
-d '{"path":"data/assets/SiYuan-Kernel"}'
# Read files from mounted volumes
curl -s 'http://127.0.0.1:6806/api/file/globalCopyFiles' \
-H 'Authorization: Token YOUR_API_TOKEN' \
-H 'Content-Type: application/json' \
-d '{"srcs":["/mnt/secrets/credentials.json"],"destDir":"data/assets"}'
Impact
- Read arbitrary files from
/opt,/usr,/home,/mnt,/mediaand any other non-denylisted path - In Docker deployments: read application source code, configs, mounted secrets
- The denylist approach is fundamentally flawed — any newly added filesystem path is accessible until explicitly blocked
Recommended Fix
Switch from a denylist to an allowlist approach. Only permit copying from the workspace directory and explicitly approved external paths:
func IsSensitivePath(p string) bool {
absPath := filepath.Clean(p)
// Allowlist: only workspace and configured safe directories
if strings.HasPrefix(absPath, WorkspaceDir) {
// Block workspace-internal sensitive paths (conf/)
if strings.HasPrefix(absPath, filepath.Join(WorkspaceDir, "conf")) {
return true
}
return false
}
// Everything outside workspace is sensitive by default
return true
}
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 3.6.1"
},
"package": {
"ecosystem": "Go",
"name": "github.com/siyuan-note/siyuan/kernel"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "3.6.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-33194"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-18T20:10:44Z",
"nvd_published_at": "2026-03-20T23:16:45Z",
"severity": "MODERATE"
},
"details": "## Summary\n\nThe `IsSensitivePath()` function in `kernel/util/path.go` uses a denylist approach that was recently expanded (GHSA-h5vh-m7fg-w5h6, commit 9914fd1) but remains incomplete. Multiple security-relevant Linux directories are not blocked, including `/opt` (application data), `/usr` (local configs/binaries), `/home` (other users), `/mnt` and `/media` (mounted volumes). The `globalCopyFiles` and `importStdMd` endpoints rely on `IsSensitivePath` as their primary defense against reading files outside the workspace.\n\n## Details\n\nCurrent denylist in `kernel/util/path.go:391-405`:\n\n```go\nprefixes := []string{\n \"/.\", // dotfiles\n \"/etc\", // system config\n \"/root\", // root home\n \"/var\", // variable data\n \"/proc\", // process info\n \"/sys\", // sysfs\n \"/run\", // runtime data\n \"/bin\", // binaries\n \"/boot\", // boot files\n \"/dev\", // devices\n \"/lib\", // libraries\n \"/srv\", // service data\n \"/tmp\", // temp files\n}\n```\n\n**NOT blocked:**\n- `/opt` \u2014 commonly contains application data, databases, credentials. In SiYuan Docker, `/opt/siyuan/` contains the application itself.\n- `/usr` \u2014 contains `/usr/local/etc`, `/usr/local/share`, custom configs\n- `/home` \u2014 other users\u0027 home directories (only `~/.ssh` and `~/.config` of the current HomeDir are blocked via separate checks, but other users\u0027 homes are accessible)\n- `/mnt`, `/media` \u2014 mounted volumes, network shares, often containing secrets\n- `/snap` \u2014 snap package data\n- `/sbin`, `/lib64` \u2014 system binaries/libraries\n\nThe `globalCopyFiles` endpoint at `kernel/api/file.go:82` uses `IsSensitivePath` as its sole path validation:\n\n```go\nif util.IsSensitivePath(absSrc) {\n // reject\n continue\n}\n// File is copied into workspace \u2014 then readable via /api/file/getFile\n```\n\n## PoC\n\n```bash\n# Read SiYuan\u0027s own application files from /opt (Docker deployment)\ncurl -s \u0027http://127.0.0.1:6806/api/file/globalCopyFiles\u0027 \\\n -H \u0027Authorization: Token YOUR_API_TOKEN\u0027 \\\n -H \u0027Content-Type: application/json\u0027 \\\n -d \u0027{\"srcs\":[\"/opt/siyuan/kernel/SiYuan-Kernel\"],\"destDir\":\"data/assets\"}\u0027\n\n# Then read the copied file from workspace\ncurl -s \u0027http://127.0.0.1:6806/api/file/getFile\u0027 \\\n -H \u0027Authorization: Token YOUR_API_TOKEN\u0027 \\\n -H \u0027Content-Type: application/json\u0027 \\\n -d \u0027{\"path\":\"data/assets/SiYuan-Kernel\"}\u0027\n\n# Read files from mounted volumes\ncurl -s \u0027http://127.0.0.1:6806/api/file/globalCopyFiles\u0027 \\\n -H \u0027Authorization: Token YOUR_API_TOKEN\u0027 \\\n -H \u0027Content-Type: application/json\u0027 \\\n -d \u0027{\"srcs\":[\"/mnt/secrets/credentials.json\"],\"destDir\":\"data/assets\"}\u0027\n```\n\n## Impact\n\n- Read arbitrary files from `/opt`, `/usr`, `/home`, `/mnt`, `/media` and any other non-denylisted path\n- In Docker deployments: read application source code, configs, mounted secrets\n- The denylist approach is fundamentally flawed \u2014 any newly added filesystem path is accessible until explicitly blocked\n\n## Recommended Fix\n\nSwitch from a denylist to an allowlist approach. Only permit copying from the workspace directory and explicitly approved external paths:\n\n```go\nfunc IsSensitivePath(p string) bool {\n absPath := filepath.Clean(p)\n\n // Allowlist: only workspace and configured safe directories\n if strings.HasPrefix(absPath, WorkspaceDir) {\n // Block workspace-internal sensitive paths (conf/)\n if strings.HasPrefix(absPath, filepath.Join(WorkspaceDir, \"conf\")) {\n return true\n }\n return false\n }\n\n // Everything outside workspace is sensitive by default\n return true\n}\n```",
"id": "GHSA-vm69-h85x-8p85",
"modified": "2026-03-25T18:12:17Z",
"published": "2026-03-18T20:10:44Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/siyuan-note/siyuan/security/advisories/GHSA-vm69-h85x-8p85"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33194"
},
{
"type": "PACKAGE",
"url": "https://github.com/siyuan-note/siyuan"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "SiYuan has an Incomplete Fix for IsSensitivePath Denylist Allows File Read from /opt, /usr, /home (GHSA-h5vh-m7fg-w5h6 Bypass)"
}
GHSA-VM6R-QWJC-7JVF
Vulnerability from github – Published: 2022-05-24 22:28 – Updated: 2022-05-24 22:28The Photo Gallery by 10Web – Mobile-Friendly Image Gallery WordPress plugin before 1.5.75 did not ensure that uploaded files are kept inside its uploads folder, allowing high privilege users to put images/SVG anywhere in the filesystem via a path traversal vector
{
"affected": [],
"aliases": [
"CVE-2021-24363"
],
"database_specific": {
"cwe_ids": [
"CWE-22"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2021-08-16T11:15:00Z",
"severity": "MODERATE"
},
"details": "The Photo Gallery by 10Web \u00e2\u20ac\u201c Mobile-Friendly Image Gallery WordPress plugin before 1.5.75 did not ensure that uploaded files are kept inside its uploads folder, allowing high privilege users to put images/SVG anywhere in the filesystem via a path traversal vector",
"id": "GHSA-vm6r-qwjc-7jvf",
"modified": "2022-05-24T22:28:59Z",
"published": "2022-05-24T22:28:59Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-24363"
},
{
"type": "WEB",
"url": "https://wpscan.com/vulnerability/1628935f-1d7d-4609-b7a9-e5526499c974"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-VM7F-687F-4R4G
Vulnerability from github – Published: 2024-01-12 18:30 – Updated: 2024-01-12 18:30NVIDIA Triton Inference Server for Linux and Windows contains a vulnerability where, when it is launched with the non-default command line option --model-control explicit, an attacker may use the model load API to cause a relative path traversal. A successful exploit of this vulnerability may lead to code execution, denial of service, escalation of privileges, information disclosure, and data tampering.
{
"affected": [],
"aliases": [
"CVE-2023-31036"
],
"database_specific": {
"cwe_ids": [
"CWE-22",
"CWE-23"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-01-12T17:15:09Z",
"severity": "HIGH"
},
"details": "NVIDIA Triton Inference Server for Linux and Windows contains a vulnerability where, when it is launched with the non-default command line option --model-control explicit, an attacker may use the model load API to cause a relative path traversal. A successful exploit of this vulnerability may lead to code execution, denial of service, escalation of privileges, information disclosure, and data tampering.",
"id": "GHSA-vm7f-687f-4r4g",
"modified": "2024-01-12T18:30:20Z",
"published": "2024-01-12T18:30:20Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-31036"
},
{
"type": "WEB",
"url": "https://nvidia.custhelp.com/app/answers/detail/a_id/5509"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Mitigation MIT-5.1
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.
- When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434.
- Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.
Mitigation MIT-15
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Mitigation MIT-20.1
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.
- Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59). This includes:
- realpath() in C
- getCanonicalPath() in Java
- GetFullPath() in ASP.NET
- realpath() or abs_path() in Perl
- realpath() in PHP
Mitigation MIT-4
Strategy: Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482].
Mitigation MIT-29
Strategy: Firewall
Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].
Mitigation MIT-17
Strategy: Environment Hardening
Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.
Mitigation MIT-21.1
Strategy: Enforcement by Conversion
- When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
- For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt". Features such as the ESAPI AccessReferenceMap [REF-185] provide this capability.
Mitigation MIT-22
Strategy: Sandbox or Jail
- Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
- OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.
- This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.
- Be careful to avoid CWE-243 and other weaknesses related to jails.
Mitigation MIT-34
Strategy: Attack Surface Reduction
- Store library, include, and utility files outside of the web document root, if possible. Otherwise, store them in a separate directory and use the web server's access control capabilities to prevent attackers from directly requesting them. One common practice is to define a fixed constant in each calling program, then check for the existence of the constant in the library/include file; if the constant does not exist, then the file was directly requested, and it can exit immediately.
- This significantly reduces the chance of an attacker being able to bypass any protection mechanisms that are in the base program but not in the include files. It will also reduce the attack surface.
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.
- In the context of path traversal, error messages which disclose path information can help attackers craft the appropriate attack strings to move through the file system hierarchy.
Mitigation MIT-16
Strategy: Environment Hardening
When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.
CAPEC-126: Path Traversal
An adversary uses path manipulation methods to exploit insufficient input validation of a target to obtain access to data that should be not be retrievable by ordinary well-formed requests. A typical variety of this attack involves specifying a path to a desired file together with dot-dot-slash characters, resulting in the file access API or function traversing out of the intended directory structure and into the root file system. By replacing or modifying the expected path information the access function or API retrieves the file desired by the attacker. These attacks either involve the attacker providing a complete path to a targeted file or using control characters (e.g. path separators (/ or \) and/or dots (.)) to reach desired directories or files.
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-76: Manipulating Web Input to File System Calls
An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.
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-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.