CVE-2026-42301 — pyp2spec
HIGHCVE-2026-42301 is a high-severity (CVSS 7.8) Improper Input Validation vulnerability in pyp2spec. A fix is available for pyp2spec — see the affected versions and patch details below.
Improper Input Validation leading to Improper Control of Generation of Code ('Code Injection') in pyp2spec
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42301.
EPSS Exploitation Probability
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
pyp2specReal-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
pyp2spec was writing PyPI package metadata (e.g. the summary field) into the generated spec file without escaping RPM macro directives. When a packager then runs rpmbuild, those directives get evaluated, so a malicious package can execute arbitrary commands on the build machine.
The macro evaluates during spec parsing, not only during the build step. Any rpm tool touching the generated spec triggers execution, rpmbuild -bs, rpmbuild --nobuild, rpm -q --specfile, so the victim doesn't need to commit to a full build before getting compromised. The realistic attack path is typosquatting or targeting a package known to be under Fedora review rather than drive-by publishing. Fedora packagers hold dist-git SSH keys, Koji build credentials, and Bodhi update credentials, so compromise of one packager's workstation enables committing malicious source to dist-git and riding it through the normal build pipeline to end users.
Patches
Patched in 0.14.1.
Workarounds
None
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyp2spec | all versions | 0.14.1pip install --upgrade 'pyp2spec==0.14.1' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyp2spec, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pyp2spec to 0.14.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42301 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.
Frequently Asked Questions
Is CVE-2026-42301 in your dependencies?
Find it across PyPI, including transitive dependencies.