vulnerability / NVI-00013033 / Revision 1
Mesop: Unauthenticated ANSI Escape Sequence Injection in CSP Reporting Endpoint
GitHub lists this reviewed advisory for mesop. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
mesop
source listed<= 1.3.3
### Summary The `/__csp__` endpoint accepts unauthenticated JSON reports and logs user-controlled values directly to stdout using `print()` without escaping control characters. A remote attacker can include ANSI/VT100 escape sequences in fields such as `blocked-uri` or `document-uri`. When the logs are viewed in an ANSI-capable terminal, these sequences can manipulate the displayed output (e.g., clear the screen, hide text, or inject misleading messages), affecting the integrity of operator-facing logs. ### Details The CSP reporting endpoint accepts arbitrary JSON and prints several request fields directly: mesop/server/static_file_serving.py ```python @app.route(prefix_base_url("/__csp__"), methods=["POST"]) def csp_report(): report = request.get_json(force=True) document_uri = report["csp-report"]["document-uri"] blocked_uri = report["csp-report"]["blocked-uri"] violated_directive = report["csp-report"]["violated-directive"] print(f"... Blocked URL: {blocked_uri} ...") ``` Since these values are written to stdout without sanitization, ANSI escape sequences supplied by a remote client are preserved and interpreted by ANSI-compatible terminals. ### PoC
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-g7f6-rxc4-qhph ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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