GHSA-QCPX-92MH-Q44F
Vulnerability from github – Published: 2026-10-08 12:34 – Updated: 2026-10-08 12:34Inefficient algorithmic complexity in the SPF macro expansion of Progressive Robot hMailServer 6.3.4 and 6.3.5 allows a remote unauthenticated attacker to consume worker-thread time by publishing a crafted SPF record. RFC 7208 section 7.1 requires a name too long to look up to lose whole labels from the left; the server did this by removing one label at a time and copying the rest of the name each time, so the work grew with the square of the expansion. An attacker who publishes an SPF record for a domain they control, with a mechanism whose domain-spec expands through macros to a name far longer than 253 characters, makes the SPF check of a message from that domain take several seconds. The expansion is bounded by SPF's own per-term and per-macro limits, so the loss of availability is partial.
{
"affected": [],
"aliases": [
"CVE-2026-107575"
],
"database_specific": {
"cwe_ids": [
"CWE-407"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-08T12:17:15Z",
"severity": "MODERATE"
},
"details": "Inefficient algorithmic complexity in the SPF macro expansion of Progressive Robot hMailServer 6.3.4 and 6.3.5 allows a remote unauthenticated attacker to consume worker-thread time by publishing a crafted SPF record. RFC 7208 section 7.1 requires a name too long to look up to lose whole labels from the left; the server did this by removing one label at a time and copying the rest of the name each time, so the work grew with the square of the expansion. An attacker who publishes an SPF record for a domain they control, with a mechanism whose domain-spec expands through macros to a name far longer than 253 characters, makes the SPF check of a message from that domain take several seconds. The expansion is bounded by SPF\u0027s own per-term and per-macro limits, so the loss of availability is partial.",
"id": "GHSA-qcpx-92mh-q44f",
"modified": "2026-10-08T12:34:27Z",
"published": "2026-10-08T12:34:27Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-107575"
},
{
"type": "WEB",
"url": "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"
},
{
"type": "WEB",
"url": "https://gitlab.com/hmailserver/hmailserver/-/work_items/74"
}
],
"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:L",
"type": "CVSS_V3"
}
]
}
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