Is CVE-2026-124016 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-124016 being exploited in the wild.

How severe is CVE-2026-124016?

Medium severity, with a CVSS score of 5.3, published 10 November 2026.

Which products and versions are affected?

Postalsys Postal-Mime before 4.2.1.

Is there a fix for CVE-2026-124016?

Yes: fixed in 4.2.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-124016 attacked?

It is attacked over the network.

Am I affected by CVE-2026-124016?

Check whether you run Postalsys Postal-Mime 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.

CVE-2026-124016: postal-mime algorithmic complexity denial of service

CVE-2026-124016 · Severity: medium · CVSS 5.3 · Published 2026-11-10

postal-mime is a Node.js library that parses email messages. An attacker can send a crafted email with deeply nested multipart structures that causes the parser to consume excessive CPU, blocking the mail server's event loop for seconds. This denial of service requires only the ability to send mail to a service using postal-mime and does not require authentication or user interaction.

Technologies: Postalsys Postal-Mime. Vendors: Postalsys.

Quick answers

Is CVE-2026-124016 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-124016 being exploited in the wild.
How severe is CVE-2026-124016?: Medium severity, with a CVSS score of 5.3, published 10 November 2026.
Which products and versions are affected?: Postalsys Postal-Mime before 4.2.1.
Is there a fix for CVE-2026-124016?: Yes: fixed in 4.2.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-124016 attacked?: It is attacked over the network.
Am I affected by CVE-2026-124016?: Check whether you run Postalsys Postal-Mime 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: 4.2.1

Technical details

The processLine() function in postal-mime performs unindexed linear comparisons of email boundary lines against all open multipart boundaries, resulting in O(depth × prefix length) cost per line. An attacker crafts a message with boundaries sharing long common prefixes plus differing suffixes, so each body line begins with "--" followed by the shared prefix but no boundary match; cost scales to O(depth × size) overall. The fix in 4.2.1 uses indexed boundary lookup instead of linear scan.

Affected products

postalsys postal-mime before 4.2.1

Timeline

2026-11-10: disclosed
2026-11-10: patched

References

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