Path traversal in apimock-server's file-serving fallback

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.2 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

The file-serving fallback joined a request-derived path onto the configured response directory and checked only that the result existed, never that it stayed inside that directory. A request containing a raw `..` segment could read any file readable by the process, returned with HTTP 200. Read-only: no write, no code execution. Exposure depends on the bind address. The default is `127.0.0.1`; deployments binding `0.0.0.0` or a LAN address are reachable from the network. Most HTTP clients normalise `..` away before sending, so reaching it requires a client that does not. All published versions before 5.19.1 are affected. Fixed in 5.19.1 by canonicalising each resolved path and rejecting anything outside its base directory. This advisory also covers `apimock` 5.x, which depends on `apimock-server`. `apimock` 4.x predates the crate split and carries its own advisory for the same issue, fixed in 4.8.1.

Published by the source

26 Aug 2026, 12:00 UTC

Last modified by the source

2 Sep 2026, 09:10 UTC

Source last checked

25 Oct 2026, 04:53 UTC

1. Revision 3 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record RUSTSEC-2026-0277

3. Revision 1 · created · 24 Oct 2026

   Published from osv record RUSTSEC-2026-0276

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# Patch Next advisory brief: GHSA-72g6-wgrg-vhm7

Advisory: Path traversal in apimock-server's file-serving fallback
IDs: GHSA-72g6-wgrg-vhm7
Record: https://patchnext.com/advisories/rustsec-2026-0276 (revision 3, source checked 25 Oct 2026, 04:53 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: apimock-server 5.19.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io apimock-server: affected >= 0.0.0-0, < 5.19.1; fixed in 5.19.1

## Suggested inspection (read-only)
- crates.io apimock-server: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on apimock-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/RUSTSEC-2026-0277 (OSV record RUSTSEC-2026-0277 lists affected ranges: crates.io apimock-server >=0.0.0-0 <5.19.1 (fixed))
- Verified: https://osv.dev/vulnerability/RUSTSEC-2026-0276 (OSV record RUSTSEC-2026-0276 lists affected ranges: crates.io apimock >=0.0.0-0 =5.0.0 <5.0.0 (fixed))

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