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CVE-2026-64619 – Unauthenticated Rate-Limit Bypass Leading to File Enumeration – FileCodeBox befo…

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Summary

CVE-2026-64619 is a high-severity rate-limit bypass vulnerability in FileCodeBox, a self-hosted anonymous file-sharing web application built on FastAPI and Vue3. The flaw exists in the IPRateLimit class, which blindly trusts attacker-supplied X-Real-IP and X-Forwarded-For HTTP headers without verifying that requests originate from a trusted reverse proxy — allowing unauthenticated remote attackers to bypass all request throttling, enumerate share codes, and retrieve other users’ files. The vulnerability is scored 8.7 (HIGH) under CVSS v4.0 and 7.5 (HIGH) under CVSS v3.1, and affects all FileCodeBox versions prior to 2.4.

Technical details

  • Root cause: The IPRateLimit class derives the client identifier from the X-Real-IP or X-Forwarded-For HTTP headers without validating that the request actually arrived through a trusted reverse proxy. Because these headers are fully attacker-controlled, a unique spoofed IP value can be supplied on every request to reset the rate counter (CWE-348: Use of Less Trusted Source).
  • Trigger conditions: No authentication, no special network position, and no prior account required. The attacker sends standard HTTP requests with manipulated headers.
  • Attack vector: Network (AV:N); low attack complexity (AC:L); no privileges required (PR:N); no user interaction (UI:N).
  • Impact — file disclosure: Share codes in FileCodeBox are short alphanumeric strings (~90,000 possible 5-digit values). With rate limiting defeated, an attacker can iterate the entire code space and retrieve every file or text snippet shared by any user on the instance.
  • Impact — upload abuse: The same header-spoofing technique defeats the upload rate limiter, enabling unauthorized storage consumption.
  • No public proof-of-concept was identified at time of publication (2026-07-20), though the technique is straightforward to reproduce from the vulnerability description alone.

Affected software

  • FileCodeBox (vendor: vastsa) — all versions before 2.4 (i.e., versions up to and including 2.3)

Severity

| Standard | Score | Rating | Vector |
|—|—|—|—|
| CVSS v4.0 | 8.7 | HIGH | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N |
| CVSS v3.1 | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |

Mitigation and recommended actions

  • Immediate: Upgrade FileCodeBox to version 2.4 or later. The fix (commit 1b6d8e7) hardens share-rate limiting and code generation so the rate limiter no longer accepts unverified client-supplied IP headers as the throttling key.
  • If immediate patching is not possible: Restrict access to the FileCodeBox instance at the network perimeter (firewall rules, reverse-proxy IP allowlists) so that only trusted users can reach the file retrieval and upload endpoints. Ensure your reverse proxy is configured to strip and re-set X-Real-IP / X-Forwarded-For headers, preventing clients from injecting arbitrary values.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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