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Not in CISA KEV
HIGH severity

CVE-2020-29651 — py

HIGHFix: pytest-dev/py#257

CVE-2020-29651 is a high-severity (CVSS 7.5) vulnerability in py. A fix is available for py — see the affected versions and patch details below.

py vulnerable to Regular Expression Denial of Service

Also known asGHSA-hj5v-574p-mj7cPYSEC-2020-92
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
4.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs92th percentile — riskier than 92% of all scored CVEsHighest risk
0.00%1.94%3.88%5.83%0.8%4.7%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2020-29651 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐍py

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

A denial of service via regular expression in the py.path.svnwc component of py (aka python-py) through 1.9.0 could be used by attackers to cause a compute-time denial of service attack by supplying malicious input to the blame functionality.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIpyall versions1.10.0pip install --upgrade 'py==1.10.0'

Affected Products

3 products · 4 configurations
OS
fedorafedoraproject
2 versions
3233
Application
zfs storage appliance kitoracle
1 version
8.8
Application
pypytest
≤ 1.9.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update py to 1.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-29651 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

UbuntuHIGH
USN-5138-1Ubuntu

Frequently Asked Questions

A denial of service via regular expression in the py.path.svnwc component of py (aka python-py) through 1.9.0 could be used by attackers to cause a compute-time denial of service attack by supplying malicious input to the blame functionality.
O3 Security · Impact-Aware SCA

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CVE-2020-29651: py DoS — Fixed in 1.10.0