How severe is CVE-2020-15163?

CVE-2020-15163 has a CVSS score of 8.2/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-15163?

CVE-2020-15163 affects the following packages: tuf (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2020-15163?

Update tuf to 0.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-15163 is resolved across your whole dependency graph.

How do I detect CVE-2020-15163 in my PyPI dependencies?

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

How do I mitigate CVE-2020-15163 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2020-15163 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-15163 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-2020-15163?

CVE-2020-15163 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 52th 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-2020-15163?

CVE-2020-15163 is classified as CWE-863 (CWE-863), CWE-345 (CWE-345). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-15163 published, and has it been updated?

CVE-2020-15163 was published on September 9, 2020 and was last updated on October 20, 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

HIGH severity

CVE-2020-15163 — tuf

HIGHFix: theupdateframework/tuf@3d342e6

CVE-2020-15163 is a high-severity (CVSS 8.2) CWE-863 vulnerability in tuf. A fix is available for tuf — see the affected versions and patch details below.

Invalid root may become trusted root in The Update Framework (TUF)

Also known asGHSA-f8mr-jv2c-v8mgPYSEC-2020-145

Published

Sep 9, 2020

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs52th percentile — riskier than 52% 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

🐍tuf

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

The Python TUF reference implementation tuf<0.12 will incorrectly trust a previously downloaded root metadata file which failed verification at download time. This allows an attacker who is able to serve multiple new versions of root metadata (i.e. by a man-in-the-middle attack) culminating in a version which has not been correctly signed to control the trust chain for future updates.

While investigating the reported vulnerability, we discovered that the detailed client workflow was not fully implemented. Specifically, for step 1.3 the newly downloaded root metadata was not being verified with a threshold of keys specified in the new root metadata file. This missing step of the client workflow has been implemented in PR #1101, which is included in v0.14.0 of tuf.

Patches

A fix, is available in version 0.12 and newer.

Workarounds

No workarounds are known for this issue.

References

Pull request resolving the invalid root becoming trusted issue PR 885
Pull request implementing self verification of newly downloaded root metadata PR 1101

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`tuf`	all versions	0.12.0`pip install --upgrade 'tuf==0.12.0'`

Affected Products

1 product · 1 configurations

Application

the update frameworklinuxfoundation

< 0.12.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tuf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update tuf to 0.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-15163 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### Impact The Python TUF reference implementation `tuf<0.12` will incorrectly trust a previously downloaded root metadata file which failed verification at download time. This allows an attacker who is able to serve multiple new versions of root metadata (i.e. by a man-in-the-middle attack) culminating in a version which has not been correctly signed to control the trust chain for future updates. While investigating the reported vulnerability, we discovered that the detailed client workflow was not fully implemented. Specifically, for step 1.3 the newly downloaded root metadata was not being