Inefficient algorithmic complexity in the webmail's message view of the REST API in Progressive Robot hMailServer 6.3.2 through 6.3.5 allows a remote unauthenticated attacker to make the webmail, the administration console and the REST API unavailable by sending a message. The route that renders a received message's HTML replaced each reference to an embedded image in place, with work that grew with the square of the number of references, and wrote the image out for every reference while counting it against its size limit only once. A message whose HTML refers to one small embedded image a very large number of times, opened in the webmail by its recipient, therefore keeps one of the listener's four worker threads busy for minutes and makes it build a document of gigabytes, so that a few such messages leave the HTTP listener unable to answer anybody.
CVE-2026-107583
Score 6.5 from GitHub Security Advisory published 2026-10-08. A secondary CVSS source baseline 6.5; sources differ by 0.0.
- Lower severity and no public exploit yet
No fix is confirmed yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for the fix.
- CVSS v3
- 6.5
- EG Score
- 6.5MEDIUMhigh confidence
- EG Risk
- 29EG Risk 29/100CISA SSVC
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity65% × 45%Exploitation0% × 40%Automatability0% × 15%CISA SSVC: Track at every mission impact level.Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix. - EPSS PROB
- 0.3%
- EPSS %ILE
- 15th
- KEV
- Not listed
CISA SSVCTrack at every mission impact level.
No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table
Published
October 8, 2026
Last Modified
October 8, 2026
Advisory Details (2)
Auto-updated Oct 8, 2026hMailServer 6.3.6 · hmailserver / hMailServer · GitLab
https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6Webmail message view: a message naming one inline image very many times held a REST worker and built a document of gigabytes (#65) · Issues · hmailserver / hMailServer · GitLab
https://gitlab.com/hmailserver/hmailserver/-/work_items/65Vendor Advisories for CVE-2026-107583(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 11× in last 7d / 11× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-10-09 20:47 UTCEG score recompute
- 2026-10-09 20:47 UTCGHSA enrichment
- 2026-10-09 20:06 UTCEPSS rescore
- 2026-10-08 21:18 UTCGHSA enrichment
- 2026-10-08 15:23 UTCEG score recompute
- 2026-10-08 15:23 UTCGHSA enrichment
- 2026-10-08 14:49 UTCEG score recompute
- 2026-10-08 14:48 UTCGHSA enrichment
- 2026-10-08 12:26 UTCEG score recompute
- 2026-10-08 11:57 UTCEG score recompute
- 2026-10-08 11:56 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
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Dependency Blast Radius
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