# CVE-2016-3957: Deserialization in n/a

> Remote attackers can execute arbitrary code by exploiting unsafe pickle deserialization in web2py session cookies if the encryption key is known.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Feb 2018
- **Updated:** 6 Aug 2024
- **Also known as:** GHSA-p6rg-cchx-f5x4, UBUNTU-CVE-2016-3957

## What is CVE-2016-3957?

CVE-2016-3957 is a critical unsafe deserialization vulnerability in n/a, published on 6 Feb 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The secure_load function in gluon/utils.py in web2py before 2.14.2 uses pickle.loads to deserialize session information stored in cookies, which might allow remote attackers to execute arbitrary code by leveraging knowledge of encryption_key.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2016-3957?

It affects 1 product.


Products: Web2py Web2py.

## How do I fix CVE-2016-3957?

Upgrade to a fixed version.

## Is CVE-2016-3957 being exploited?

There is no known exploitation of CVE-2016-3957 in the wild and no public exploit code.

Public exploit code:

- web2py/web2py @ e94946d (github_poc): https://github.com/sj/web2py-e94946d-CVE-2016-3957

## Other vulnerabilities in n/a

- [CVE-2023-45158](https://insights.sbomify.com/CVE-2023-45158/): Command injection in web2py (critical 9.8)
- [CVE-2016-3953](https://insights.sbomify.com/CVE-2016-3953/): web2py remote code execution via hardcoded encryption key in session.connect function (critical 9.8)
- [CVE-2016-10321](https://insights.sbomify.com/CVE-2016-10321/): web2py is vulnerable to password brute-force attack (critical 9.8)
- [CVE-2016-4808](https://insights.sbomify.com/CVE-2016-4808/): Web2py Cross-Site Request Forgery vulnerability (high 8.8)
- [CVE-2016-3952](https://insights.sbomify.com/CVE-2016-3952/): Information disclosure in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-3957 and fix it if it is affected.

What it is: CVE-2016-3957 is a critical unsafe deserialization vulnerability in n/a, published on 6 Feb 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2016-3957 in the wild and no public exploit code.

Affected product: n/a. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2016-3957/ (Markdown: https://insights.sbomify.com/CVE-2016-3957/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-3957
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-3957
- OSV: https://osv.dev/vulnerability/CVE-2016-3957

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From sbomify Insights: https://insights.sbomify.com/CVE-2016-3957/
Summaries are generated and may contain mistakes; the official description above is the record.