CVE-2019-9153 is a high-severity (CVSS 7.5) CWE-347 vulnerability in openpgp. 1 public exploit reference exists, so weaponization risk is real. A fix is available for openpgp — see the affected versions and patch details below.
Message Signature Bypass in openpgp
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2019-9153 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
openpgpnpmDescription
Versions of openpgp prior to 4.2.0 are vulnerable to Message Signature Bypass. The package fails to verify that a message signature is of type text. This allows an attacker to to construct a message with a signature type that only verifies subpackets without additional input (such as standalone or timestamp). For example, an attacker that captures a standalone signature packet from a victim can construct arbitrary signed messages that would be verified correctly.
Recommendation
Upgrade to version 4.2.0 or later.
If you are upgrading from a version <4.0.0 it is highly recommended to read the High-Level API Changes section of the openpgp 4.0.0 release: https://github.com/openpgpjs/openpgpjs/releases/tag/v4.0.0
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | openpgp | all versions | 4.2.0npm install openpgp@4.2.0 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openpgp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update openpgp to 4.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-9153 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2019-9153 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2019-9153. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2019-9153 in your dependencies?
O3 Security finds CVE-2019-9153 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.