CVE-2026-103649

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-10-08. A secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
7.5EG
EchelonGraph verdictPlan mitigationSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 7.5Exploit: None knownExposed services: Not assessed

No fix is confirmed yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for the fix.

Missing network timeouts in the Linux builds of Progressive Robot hMailServer 6.3.0 through 6.3.5 allow a remote attacker to hold server threads indefinitely and so stop outbound mail delivery (denial of service). The server set its socket timeouts in the form Windows takes, which Linux refuses, and its HTTPS clients read without a deadline, so a peer that accepts a connection and then sends nothing held the waiting thread for as long as the connection stayed open. The MTA-STS policy fetch, enabled by default, is made during outbound delivery to mta-sts., so anyone who can make the server deliver mail to a domain they control - for example as the envelope sender of a message that bounces - can hold delivery threads until outbound delivery stops. The same flaw affects the DANE TLSA query, the OAuth2 token request, the ACME client, and the ManageSieve and metrics listeners, which a silent client stops from serving anyone else. Windows builds are not affected.

CVSS v3
7.5
EG Score
7.5HIGHhigh confidence
EG Risk
49
EG Risk 49/100CISA 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 computed
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.
EPSS PROB
0.3%
EPSS %ILE
17th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.

Exploitation none (CISA Vulnrichment) · Automatable yes (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, 2026
No fix on record yet.
generic

hMailServer 6.3.6 · hmailserver / hMailServer · GitLab

https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6
generic

Linux: some network waits had no timeout, so a remote peer could hold delivery threads (6.3.0 to 6.3.5) (#53) · Issues · hmailserver / hMailServer · GitLab

https://gitlab.com/hmailserver/hmailserver/-/work_items/53

Vendor Advisories for CVE-2026-103649(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 12× in last 7d / 12× 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.

  1. 2026-10-09 20:49 UTCEG score recompute
  2. 2026-10-09 20:49 UTCGHSA enrichment
  3. 2026-10-09 20:06 UTCEPSS rescore
  4. 2026-10-09 09:04 UTCGHSA enrichment
  5. 2026-10-08 21:19 UTCGHSA enrichment
  6. 2026-10-08 15:23 UTCEG score recompute
  7. 2026-10-08 15:23 UTCGHSA enrichment
  8. 2026-10-08 14:53 UTCEG score recompute
  9. 2026-10-08 14:52 UTCGHSA enrichment
  10. 2026-10-08 11:24 UTCEG score recompute
  11. 2026-10-08 10:57 UTCEG score recompute
  12. 2026-10-08 10:56 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-103649?
CVE-2026-103649 is a high vulnerability published on October 8, 2026. Missing network timeouts in the Linux builds of Progressive Robot hMailServer 6.3.0 through 6.3.5 allow a remote attacker to hold server threads indefinitely and so stop outbound mail delivery (denial of service). The server set its socket timeouts in the form Windows takes, which Linux refuses,…
When was CVE-2026-103649 disclosed?
CVE-2026-103649 was first published on October 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-103649 actively exploited?
CVE-2026-103649 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (17th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-103649?
CVE-2026-103649 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-103649?
No fix for CVE-2026-103649 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-103649 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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