CVE-2023-41037 is a medium-severity (CVSS 4.3) 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.
Cleartext Signed Message Signature Spoofing in openpgpjs
Exploitation Status
No confirmed exploitation observed yet
- 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-2023-41037.
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-2023-41037 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 378,567 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
Impact
OpenPGP Cleartext Signed Messages are cryptographically signed messages where the signed text is readable without special tools:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
This text is signed.
-----BEGIN PGP SIGNATURE-----
wnUEARMIACcFgmTkrNAJkInXCgj0fgcIFiEE1JlKzzDGQxZmmHkYidcKCPR+
BwgAAKXDAQDWGhI7tPbhB+jlKwe4+yPJ+9X8aWDUG60XFNi/w8T7ZgEAsAGd
WJrkm/H5AXGZsqyqqO6IWGF0geTCd4mWm/CsveM=
-----END PGP SIGNATURE-----
These messages typically contain a "Hash: ..." header declaring the hash algorithm used to compute the signature digest. OpenPGP.js up to v5.9.0 ignored any data preceding the "Hash: ..." texts when verifying the signature. As a result, malicious parties could add arbitrary text to a third-party Cleartext Signed Message, to lead the victim to believe that the arbitrary text was signed.
A user or application is vulnerable to said attack vector if it verifies the CleartextMessage by only checking the returned verified property, discarding the associated data information, and instead visually trusting the contents of the original message:
const cleartextMessage = `
-----BEGIN PGP SIGNED MESSAGE-----
This text is not signed but you might think it is. Hash: SHA256
This text is signed.
-----BEGIN PGP SIGNATURE-----
wnUEARMIACcFgmTkrNAJkInXCgj0fgcIFiEE1JlKzzDGQxZmmHkYidcKCPR+
BwgAAKXDAQDWGhI7tPbhB+jlKwe4+yPJ+9X8aWDUG60XFNi/w8T7ZgEAsAGd
WJrkm/H5AXGZsqyqqO6IWGF0geTCd4mWm/CsveM=
-----END PGP SIGNATURE-----
`;
const message = await openpgp.readCleartextMessage({ cleartextMessage });
const verificationResult = await verifyCleartextMessage({ message, verificationKeys });
console.log(await verificationResult.verified); // output: true
console.log(verificationResult.data); // output: 'This text is signed.'
Since verificationResult.data would always contain the actual signed data, users and apps that check this information are not vulnerable.
Similarly, given a CleartextMessage object, retrieving the data using getText() or the text field returns only the contents that are considered when verifying the signature.
Finally, re-armoring a CleartextMessage object (using armor() will also result in a "sanitised" version, with the extraneous text being removed.
Because of this, we consider the vulnerability impact to be very limited when the CleartextMessage is processed programmatically; this is reflected in the Severity CVSS assessment, specifically in the scope's score ("Unchanged").
Patches
- v5.10.1 (current stable version) will reject messages when calling
openpgp.readCleartextMessage() - v4.10.11 (legacy version) will reject messages when calling
openpgp.cleartext.readArmored()
Workarounds
Check the contents of verificationResult.data to see what data was actually signed, rather than visually trusting the contents of the armored message.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | openpgp | all versions | 4.10.11npm install openpgp@4.10.11 |
| 📦npm | openpgp | ≥ 5.0.0&&< 5.10.1 | 5.10.1npm install openpgp@5.10.1 |
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 4.10.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-41037 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-2023-41037 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-41037. 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-2023-41037 in your dependencies?
O3 Security finds CVE-2023-41037 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.