Vulnerability in Postalsys Postal-Mime
CVE-2026-124016
postal-mime before 4.2.1 contains an algorithmic complexity denial of service vulnerability that allows unauthenticated remote attackers to cause excessive CPU consumption in the PostalMime.processLine() function by crafting deeply nested multipart email messages with boundary lines sharing long prefixes with open boundaries. Attackers can deliver a malicious email with nesting up to the default maxNestingDepth of 256, causing per-line parsing cost to scale as O(depth x shared prefix length) and blocking the Node.js event loop for seconds per message.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/postalsys/postal-mime/security/advisories/GHSA-q8wm-54mj-r36p (vendor-advisory)
- github.com/postalsys/postal-mime/releases/tag/v4.2.1 (release-notes, patch)
- www.vulncheck.com/advisories/postal-mime-algorithmic-complexity-dos-via-process… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-124016?
- CVE-2026-124016 is a medium-severity vulnerability in Postalsys Postal-Mime, classified under Inefficient Algorithmic Complexity. CVSS score: 5.3/10. Published 2026-11-10.
- How severe is CVE-2026-124016?
- Medium severity. CVSS v3 base score is 5.3 out of 10.