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's own per-term and per-macro limits, so the loss of availability is partial.
Metrics
Affected Vendors & Products
References
History
Thu, 08 Oct 2026 15:15:00 +0000
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| Metrics |
ssvc
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Thu, 08 Oct 2026 13:30:00 +0000
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| First Time appeared |
Progressive Robot
Progressive Robot hmailserver |
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| Vendors & Products |
Progressive Robot
Progressive Robot hmailserver |
Thu, 08 Oct 2026 12:00:00 +0000
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| Description | 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's own per-term and per-macro limits, so the loss of availability is partial. | |
| Title | Inefficient Algorithmic Complexity in hMailServer | |
| Weaknesses | CWE-407 | |
| References |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitLab
Published: 2026-10-08T11:46:46.082Z
Updated: 2026-10-08T14:17:04.989Z
Reserved: 2026-10-08T10:51:40.639Z
Link: CVE-2026-107575
Updated: 2026-10-08T14:17:00.390Z
Status : Deferred
Published: 2026-10-08T12:17:15.333
Modified: 2026-10-08T21:02:43.860
Link: CVE-2026-107575
No data.