Nodemailer: Quadratic (O(n^2)) DKIM header unfolding lets a large folded header cause remote denial of service during signing

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.0038, the 32nd percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

1. 31 Oct 2026, 13:33 UTC First seen by agentprime
2. 31 Oct 2026, 13:33 UTC Confirmed by OSV

Sources

• GitHub Advisory Database: GHSA-39m8-27wv-hr27
• OSV: GHSA-39m8-27wv-hr27
• github.com/nodemailer/nodemailer/security/advisories/GHSA-39m8-27wv-hr27
• nvd.nist.gov/vuln/detail/CVE-2026-110871
• github.com/nodemailer/nodemailer/commit/28a5909cec27646cb001dc7e97a8f5d26c973078
• github.com/nodemailer/nodemailer
• github.com/nodemailer/nodemailer/releases/tag/v10.0.10
• www.vulncheck.com/advisories/nodemailer-3.0.0-before-10.0.10-quadratic-dkim-header-unfolding-denial-of-service

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.