How severe is CVE-2023-40587?

CVE-2023-40587 has a CVSS score of 4.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2023-40587?

CVE-2023-40587 affects the following packages: pyramid (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2023-40587?

Update pyramid to 2.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-40587 is resolved across your whole dependency graph.

How do I detect CVE-2023-40587 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyramid, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2023-40587 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2023-40587 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-40587 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-40587?

CVE-2023-40587 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 55th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2023-40587?

CVE-2023-40587 is classified as Path Traversal (CWE-22). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2023-40587 published, and has it been updated?

CVE-2023-40587 was published on August 25, 2023 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

MEDIUM severity

CVE-2023-40587 — pyramid

MEDIUMFix: Pylons/pyramid@347d775

CVE-2023-40587 is a medium-severity (CVSS 4.3) Path Traversal vulnerability in pyramid. A fix is available for pyramid — see the affected versions and patch details below.

Pyramid static view path traversal up one directory

Also known asGHSA-j8g2-6fc7-q8f8PYSEC-2026-1840

Published

Aug 25, 2023

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs55th percentile — riskier than 55% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐍pyramid

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Impact

This impacts users of Python 3.11 that are using a Pyramid static view with a full filesystem path and have a index.html file that is located exactly one directory above the location of the static view's file system path. No further path traversal exists, and the only file that could be disclosed accidentally is index.html.

Example:

config.add_static_view(name='static', path='/usr/src/app/static', cache_max_age=0)

And directory tree:

/usr/src/app \
              | - static \
                          | - file.css
                          | - index.html
                          | - ...
              | - index.html <-- (this file could be disclosed with this bug)

Patches

Pyramid now will reject any path that contains a null-byte out of caution. While valid in directory/file names, we would strongly consider it a mistake to use null-bytes in naming files/directories.

Secondly, Python 3.11, and 3.12 has fixed the underlying issue in os.path.normpath to no longer truncate on the first 0x00 found, returning the behavior to pre-3.11 Python, un an as of yet unreleased version, see:

At the time the following Python versions are not fixed:

Python 3.11.0 to 3.11.4
Python 3.12.0a1 to 3.12.0rc1

Fixes will be available in: Python 3.12.0rc2 or 3.11.5.

Please note that release candidates of Python are not production ready and should not be used for production workloads.

Workarounds

Use a version of Python 3 that is not affected. Downgrade to Python 3.10 series temporarily, or wait till Python 3.11.5 is released and upgrade to the latest version of Python 3.11 series.

References

https://owasp.org/www-community/attacks/Path_Traversal
VN: JVN#41113329
TN: JPCERT#93311166

Thanks

Masashi Yamane of LAC Co., Ltd

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`pyramid`	≥ 2.0.0&&< 2.0.2	2.0.2`pip install --upgrade 'pyramid==2.0.2'`

Affected Products

2 products · 3 configurations

Application

pyramidagendaless

≥ 2.0 && < 2.0.2

range

fedorafedoraproject

2 versions

3839

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyramid, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pyramid to 2.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-40587 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

### Impact This impacts users of Python 3.11 that are using a Pyramid static view with a full filesystem path and have a `index.html` file that is located exactly one directory above the location of the static view's file system path. No further path traversal exists, and the only file that could be disclosed accidentally is `index.html`. Example: ``` config.add_static_view(name='static', path='/usr/src/app/static', cache_max_age=0) ``` And directory tree: ``` /usr/src/app \ | - static \ | - file.css | - index.html

O3 Security · Impact-Aware SCA

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