GHSA-2C7F-JHWJ-7Q7H
Vulnerability from github – Published: 2026-10-08 12:34 – Updated: 2026-10-08 12:34Inefficient algorithmic complexity in the JSON reader of Progressive Robot hMailServer allows a remote unauthenticated attacker to make the mail services unavailable. Reading a JSON object kept the first of each duplicated member name by searching the members already read, so an object of N distinct member names cost O(N^2): 1 MB took 8.9 seconds and 4 MB took 300 seconds against the affected code. A remote attacker reaches the reader without an account by mailing a crafted TLS-RPT report (up to 16 MB after decompression) to a hosted domain's published report mailbox, which is read on a delivery thread; a few such reports hold every delivery thread (ten by default), so the server delivers no mail, local or outbound, for over an hour per report. A signed-in account reaches the same 16 MB body through the webmail's own REST routes, holding the REST API's own worker threads. Where no report mailbox is configured, the unauthenticated REST sign-in routes that read a JSON body are capped at 64 KB and are not affected.
{
"affected": [],
"aliases": [
"CVE-2026-107574"
],
"database_specific": {
"cwe_ids": [
"CWE-407"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-08T12:17:15Z",
"severity": "HIGH"
},
"details": "Inefficient algorithmic complexity in the JSON reader of Progressive Robot hMailServer allows a remote unauthenticated attacker to make the mail services unavailable. Reading a JSON object kept the first of each duplicated member name by searching the members already read, so an object of N distinct member names cost O(N^2): 1 MB took 8.9 seconds and 4 MB took 300 seconds against the affected code. A remote attacker reaches the reader without an account by mailing a crafted TLS-RPT report (up to 16 MB after decompression) to a hosted domain\u0027s published report mailbox, which is read on a delivery thread; a few such reports hold every delivery thread (ten by default), so the server delivers no mail, local or outbound, for over an hour per report. A signed-in account reaches the same 16 MB body through the webmail\u0027s own REST routes, holding the REST API\u0027s own worker threads. Where no report mailbox is configured, the unauthenticated REST sign-in routes that read a JSON body are capped at 64 KB and are not affected.",
"id": "GHSA-2c7f-jhwj-7q7h",
"modified": "2026-10-08T12:34:26Z",
"published": "2026-10-08T12:34:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-107574"
},
{
"type": "WEB",
"url": "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"
},
{
"type": "WEB",
"url": "https://gitlab.com/hmailserver/hmailserver/-/work_items/76"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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