eml_parser: DoS via deeply nested parens in Received headers

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-55620
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-25 19:16:50 UTC
Updated2026-08-26 16:16:28 UTC
Descriptioneml_parser serves as a python module for parsing eml files and returning various information found in the e-mail as well as computed information. Prior to 3.0.2, eml_parser.routing.noparenthesis in eml_parser/routing.py removes parenthesized CFWS comments from Received: headers with a regex-based fix-point loop whose running time is quadratic in the nesting depth. A single Received: header with 5,000 nested parentheses causes approximately 1.3 seconds of CPU saturation per parsed message, and doubling the nesting depth approximately quadruples the running time. An attacker can submit relatively small EML files that consume multiple seconds of processing time, causing worker latency, queue backpressure, and possible service-level outages in synchronous gateways, sandboxes, and real-time triage pipelines. This issue is fixed in version 3.0.2.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.003660000 probability, percentile 0.293490000 (date 2026-08-26)

Problem Types: CWE-770 | CWE-1124 | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling | CWE-1124 CWE-1124: Excessively Deep Nesting

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA GOVCERT-LU Eml Parser affected < 3.0.2 Not specified

References

ReferenceSourceLinkTags
github.com/GOVCERT-LU/eml_parser/security/advisories/GHSA-g7gc-gmgp-wgqg [email protected] github.com
github.com/GOVCERT-LU/eml_parser/pull/90 [email protected] github.com
github.com/GOVCERT-LU/eml_parser/commit/746a69f86443eb0b6a47f77db3cfe727... [email protected] github.com
github.com/GOVCERT-LU/eml_parser/releases/tag/v3.0.2 [email protected] github.com
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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