CVE-2026-110869 nodemailer CVE debrief

Who should care

Defenders responsible for Node.js applications using Nodemailer for email processing should assess exposure and prioritize updates to mitigate potential denial of service attacks. This includes reviewing Node.js event loop handling in email processing and monitoring for potential SMTP AUTH Mechanism Detection Regexes attacks. Defenders should also verify and update Nodemailer versions to 10.0.13 or later, especially in environments where Node.js is used.

Why it matters

Defenders should prioritize verifying and updating Nodemailer versions to 10.0.13 or later, especially in environments where Node.js is used for email processing, to mitigate potential denial of service attacks.

• Potential for extended Node.js event loop blocking
• Denial of service attacks via malicious SMTP servers
• Need for verification of Nodemailer version and Node.js event loop handling

Technical summary

The vulnerability in Nodemailer 3.0.0 before 10.0.13 is caused by overlapping whitespace sub-patterns in four AUTH mechanism detection regexes, which can lead to quadratic backtracking and block the Node.js event loop. A malicious SMTP server can reply to EHLO with 250-AUTH, a long whitespace run and a non-matching token, blocking the Node.js event loop for tens of seconds to hours before authentication. Defenders should prioritize verifying and updating Nodemailer versions to 10.0.13 or later, especially in environments where Node.js is used for email processing.

Defensive priority

Defenders should prioritize verifying and updating Nodemailer versions to 10.0.13 or later, especially in environments where Node.js is used for email processing.

Recommended defensive actions

• Verify Nodemailer version and update to 10.0.13 or later
• Review Node.js event loop handling in email processing
• Monitor for potential SMTP AUTH Mechanism Detection Regexes attacks
• Perform vulnerability scanning to identify exposed systems
• Implement compensating controls for exposed systems
• Review and update incident response plans
• Track and document remediation efforts

Evidence notes

The CVE record and source item provide details on the vulnerability, including its impact on Node.js event loops and potential for denial of service. The vulnerability is caused by overlapping whitespace sub-patterns in four AUTH mechanism detection regexes, which can lead to quadratic backtracking and block the Node.js event loop. Defenders should verify and update Nodemailer versions to 10.0.13 or later, especially in environments where Node.js is used for email processing. Evidence is limited to the CVE record and source item.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.