dbcve.org
Path TraversalWeakness · CWE-22

CVE-2026-53951

HIGH · 8.8 CVSS v4.0 Published 2026-07-08
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
91/100
Remediation priority · Urgent
No privileges 6 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Copier is a library and CLI app for rendering project templates. In versions 9.5.0 through 9.15.1, the `trust` setting's prefix match (`copier/_settings.py`) compares the template URL against a trusted prefix with a raw `str.startswith` and no path normalization, while the URL is normalized when the template is actually fetched (`Path.resolve()` for local paths; libcurl dot-segment removal for `https`). A template reference that textually starts with a trusted prefix but contains `..` is therefore granted trust yet resolves to a different, attacker-controlled template, whose `tasks` / `migrations` / `jinja_extensions` then run without the `--trust` prompt — arbitrary command execution. Version 9.15.2 patches the issue.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The Copier library versions 9.5.0-9.15.1 has a path traversal vulnerability in the trust setting validation. The code uses raw str.startswith() to check if a template URL matches a trusted prefix without normalizing paths first. An attacker can bypass this check by using path traversal sequences (../) in a template URL that textually starts with a trusted prefix but resolves to an attacker-controlled template, causing arbitrary command execution via untrusted tasks/migrations/jinja_extensions without the --trust prompt.

MitigationUpgrade to Copier version 9.15.2 or later which includes proper path normalization in the trust prefix matching. Review any templates that use the trust feature to ensure no malicious templates were loaded during the vulnerable period.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
None
Authentication
X
User interaction
P
Scope
X

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Copier version
    Run `copier --version` or `pip show copier` to retrieve the installed version number
    Affected if The version is 9.5.0 through 9.15.1 inclusive
  2. Review project-specific Copier configuration
    Check for a `copier.yml` or `copier.yaml` file in your project root, or look for a `.copier-answers.yml` file that may contain template URLs and trust settings
    Affected if The configuration references external template URLs and uses trust settings (such as trust for tasks, migrations, or jinja_extensions) without explicit user confirmation at runtime
  3. Audit template sources used in past runs
    Review any copier answers files, CI/CD logs, or scripts that invoke copier to identify which template URLs were used
    Affected if Any template URL contains path traversal sequences (../) or resolves to a location outside the declared trusted prefix
  4. Check for automated Copier invocations
    Search for scripts, CI pipelines, or cron jobs that run copier without interactive confirmation or that use flags like --trust
    Affected if Copier is run in automated contexts where the --trust prompt would be bypassed, enabling the vulnerability to be triggered without user awareness

You are affected if Copier version 9.5.0-9.15.1 is installed and you have used trusted template URLs (for tasks, migrations, or jinja_extensions) in automated or non-interactive contexts where path traversal could have been exploited.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Copier version 9.15.2 or later which includes proper path normalization in the trust prefix matching. Review any templates that use the trust feature to ensure no malicious templates were loaded during the vulnerable period.

Recommended fix High confidence

Upgrade to Copier version 9.15.2 or later

  1. 1. Check the current installed version of Copier: pip show copier or copier --version
  2. 2. If running a version between 9.5.0 and 9.15.1 inclusive, upgrade to version 9.15.2 or later
  3. 3. Run: pip install --upgrade copier>=9.15.2
  4. 4. Verify the upgrade was successful: pip show copier to confirm version 9.15.2 or newer is installed
  5. 5. Test that templates with paths containing '..' are no longer incorrectly granted trust status

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-53951 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-53951 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data