CVE-2026-107575: medium-severity vulnerability in Progressive Robot Ltd hMailServer
Inefficient Algorithmic Complexity in hMailServer
Published
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.3epss 0.4%
exploitation probability
0.4%top 69% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Affected products
Progressive Robot Ltd · hMailServerRelated CVEs — Progressive Robot Ltd hMailServer
In the same product, most dangerous first.
CVE-2026-100741CRITICALImproper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection') in hMailServerEPSS 1.7%CVE-2026-107585MEDIUMAllocation of Resources Without Limits or Throttling in hMailServerEPSS 0.4%CVE-2026-107576HIGHInefficient Algorithmic Complexity in hMailServerEPSS 0.4%CVE-2026-107577HIGHLoop with Unreachable Exit Condition ('Infinite Loop') in hMailServerEPSS 0.4%CVE-2026-107574HIGHInefficient Algorithmic Complexity in hMailServerEPSS 0.4%CVE-2026-107579HIGHInefficient Algorithmic Complexity in hMailServerEPSS 0.3%