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CVE-2026-107575

5.3 · MEDIUM

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…

Published Oct 8, 2026CWE-407EPSS 0.39%

Overview

CVE-2026-107575 is a medium-severity vulnerability. It was published on October 8, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgitlab.com/hmailserver/hmailserver/-/releases/v6.3.6Refgitlab.com/hmailserver/hmailserver/-/work_items/74

How CyberStrike helps

Frequently asked questions

What is CVE-2026-107575?

CVE-2026-107575 is a medium-severity vulnerability. It was published on October 8, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-107575?

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-107575?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-107575?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-107575 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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