Quick answers
- Is This vulnerability exploited in the wild?
- No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
- How severe is This vulnerability?
- High severity, with a CVSS score of 7.5, published 13 September 2026.
- Which products and versions are affected?
- Nodemailer 9.1.0 through 10.0.4; nodemailer (npm) >= 9.1.0, <= 10.0.4.
- Is there a fix for This vulnerability?
- Yes: fixed in 10.0.5. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is This vulnerability attacked?
- It is attacked over the network.
- Am I affected?
- Check whether you run Nodemailer or nodemailer (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: 10.0.5
Technical details
The vulnerability is a CWE-407 inefficient algorithmic complexity issue in the addressparser component's join logic. When parsing addresses with comment-separated atoms (e.g., "a@b(c)@b(c)@b(c)..."), the parser accumulates atoms into a growing string and calls slice(-1) on the entire accumulated string on every token to check the last character, resulting in O(n²) time complexity. The flaw is reachable remotely via mailparser, which parses inbound email headers without authentication; a ~640 KB malicious address header can block the event loop for approximately 7 seconds.
Affected products
- Nodemailer Nodemailer 9.1.0 through 10.0.4
Timeline
- 2026-09-11: disclosed
- 2026-09-13: advisory
- 2026-09-13: patched: v10.0.5 released