Allocation of resources without limits in the JSON reader of Progressive Robot hMailServer 6.3.2 through 6.3.7 allows a remote attacker to exhaust the server's memory and hold its threads, making mail delivery, the REST API and the webmail unavailable. The reader built a tree of values far larger than the text it read, copying each value into every level above it, and set no bound on the number of values, so a single JSON document of many small values, within the 16 MB the server reads, raised the service's memory by about 2 GB and held one thread for seconds to minutes. From 6.3.4 a remote unauthenticated attacker reaches the reader by mailing such a document as a TLS-RPT report, up to 16 MB once decompressed, to a hosted domain's report mailbox, where an administrator has set one; it is read on a mail delivery thread (ten by default), and those threads deliver all mail, local and outbound. From 6.3.4 it is also reached without an account through the reply to a password-protected message, with the message's link alone, where the REST API is on (it is off by default) and a public base URL for such links is set; and by any account, from 6.3.2 through the webmail's send and draft routes and from 6.3.4 through its other routes granted 16 MB and the send API; the webmail's send, draft and settings routes parsed the body again for each member read. The REST API serves every request on four worker threads, in the process that also serves SMTP, IMAP and POP3, so a few such documents at once make it unavailable and can exhaust the machine's memory and end the whole service. This is a separate defect from CVE-2026-107574, the reader's handling of duplicate member names, fixed in 6.3.6.
CVE-2026-126613
“—” beside the score: it is equal to the CVSS score beside it.
Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-11-11. A secondary CVSS source baseline 7.5; sources differ by 0.0.
Also known asEUVD-2026-123326 (ENISA EUVD) · GHSA-68qj-r5q8-pvm5 (GitHub Security Advisories)Source: ENISA EUVD
- High severity, but no confirmed exploitation yet
Upgrade to hMailServer 6.3.8, whose JSON reader moves each value into its place rather than copying it, and in which a REST request body is parsed within the bounds before any handler reads it, and the shared member rea… (from the CVE record's solution, GitLab Inc.) — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHhigh confidence
- EG Risk
- 34EG Risk 34/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity75% × 45%Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.5% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability0% × 15%CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: Upgrade to hMailServer 6.3.8, whose JSON reader moves each value into its place rather than copying it, and in which a REST request body is parsed within the bounds before any handler reads it, and the shared member rea… (from the CVE record's solution, GitLab Inc.). Apply it within your standard update timelines. - EPSS PROB
- 0.5%
- EPSS %ILE
- 41st
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
Upgrade to hMailServer 6.3.8, whose JSON reader moves each value into its place rather than copying it, and in which a REST request body is parsed within the bounds before any handler reads it, and the shared member rea… (from the CVE record's solution, GitLab Inc.). Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
November 11, 2026
Last Modified
November 12, 2026
Advisory Details (2)
Auto-updated Nov 11, 2026hMailServer 6.3.8 · hmailserver / hMailServer · GitLab
https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.8JSON reader: a document of many values, within the 16 MB a REST route or a mailed TLS-RPT report may carry, built a tree of gigabytes and held a REST worker or a delivery thread for seconds to minutes (6.3.2 to 6.3.7) (#110) · Issues · hmailserver / hMailServer · GitLab
https://gitlab.com/hmailserver/hmailserver/-/work_items/110Vendor Advisories for CVE-2026-126613(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 6× in last 7d / 6× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.
- 2026-11-12 19:08 UTCEchelonGraph re-scored
- 2026-11-12 19:08 UTCGHSA enrichmentGHSA-68qj-r5q8-pvm5 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-11-12 16:33 UTCEPSS rescoreEPSS 0.5% · 41st percentile
- 2026-11-11 16:38 UTCEPSS rescoreEPSS 0.5% · 41st percentile
- 2026-11-11 09:46 UTCEchelonGraph re-scored
- 2026-11-11 09:46 UTCGHSA enrichmentGHSA-68qj-r5q8-pvm5 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-11-11 09:27 UTCEchelonGraph re-scored
- 2026-11-11 09:00 UTCENISA EUVD ID recordedEUVD-2026-123326 · Source: ENISA EUVD
- 2026-11-11 08:39 UTCEchelonGraph re-scoredFirst assessed: 7.5 HIGH
- 2026-11-11 08:39 UTCMITRE cvelistV5first tracked
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