CVE-2026-107572 (GCVE-0-2026-107572)
Vulnerability from cvelistv5 – Published: 2026-10-08 11:46 – Updated: 2026-10-08 17:35
VLAI
EPSS
VEX
Title
Inefficient Regular Expression Complexity in hMailServer
Summary
Inefficient complexity in the Sieve filter evaluation of Progressive Robot hMailServer 6.2.24 through 6.3.5 allows an authenticated account holder to make the mail services unavailable with their own filter. A ':matches' pattern was matched by a backtracking descent whose time grew with the matched value's length raised to the number of wildcards, so a pattern such as '*a*a*a*b' over 800 characters took 44 seconds; and 'deleteheader' erased the fields it removed one at a time, so removing many fields of one name over a message's header cost O(N^2) (80,000 fields took 18.8 seconds). Sieve filters run on the small, shared delivery thread pool, so an account holder whose active script does this, fed a few messages they can send themselves, empties the pool and stops delivery for the whole server. The script is the account holder's own and cannot be set for another user.
Severity
6.5 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-08 17:35 UTC
CWE
- CWE-1333 - Inefficient Regular Expression Complexity
Assigner
References
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Progressive Robot Ltd | hMailServer |
Affected:
6.2.24 , < 6.3.6
(semver)
|
guessed |
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Sightings
| Author | Source | Type | Date | Other |
|---|
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Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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They have not been verified by an analyst and are provided for guidance only.
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Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.