CVE-2026-124016 json
postal-mime < 4.2.1 Algorithmic Complexity DoS via processLine
published 2d ago modified yesterday also EUVD-2026-122665 , GHSA-q8wm-54mj-r36p
Unreviewed: the maintainers' own advisory
Published by the maintainers on their GitHub repository postalsys/postal-mime. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.
- cvss
- 5.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.6%
- EPSS 0.6% chance of exploitation in 30 days, percentile 49%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- npm postal-mime 4.2.1
- postalsys postal-mime 4.2.1
Is CVE-2026-124016 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- yesterday
Exploit prediction
0.61% chance of exploitation in the next 30 days, higher than 49% of all scored CVEs (FIRST EPSS, 2026-11-11).
Exploits and checks
- github.com https://github.com/postalsys/postal-mime/security/advisories/GHSA-q8wm-54mj-r36p referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 6.9 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N |
| CNA | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| CNA | 4.0 | 6.9 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | postal-mime | <=4.2.0 |
4.2.1 |
Affected products
- postalsys postal-mime
Classification
- Weakness
-
- CWE-407 Inefficient Algorithmic Complexity
References
-
github.com
/postalsys/postal-mime/releases/tag/v4.2.1
release-notes, patch
-
github.com
/postalsys/postal-mime/security/advisories/GHSA-q8wm-54mj-r36p
vendor-advisory, exploit, advisory
-
vulncheck.com
/advisories/postal-mime-algorithmic-complexity-dos-via-processline
third-party-advisory
Sources
- CVE List CVE-2026-124016
- NVD CVE-2026-124016
- Maintainer advisory GHSA-q8wm-54mj-r36p
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
The maintainers of postalsys/postal-mime published their own advisory on GitHub. Reviewed sources take precedence over it.