# CVE-2026-107575: Inefficient Algorithmic Complexity in hMailServer

> Remote attackers can cause partial denial of service in hMailServer by publishing crafted SPF records that trigger inefficient algorithmic complexity during macro expansion.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 Oct 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-qcpx-92mh-q44f

## What is CVE-2026-107575?

CVE-2026-107575 is a medium-severity denial of service vulnerability in Progressive Robot Ltd hMailServer, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-107575?


## How do I fix CVE-2026-107575?

No fix has been published for CVE-2026-107575 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-107575 being exploited?

There is no known exploitation of CVE-2026-107575 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-107575 and fix it if it is affected.

What it is: CVE-2026-107575 is a medium-severity denial of service vulnerability in Progressive Robot Ltd hMailServer, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-107575 in the wild and no public exploit code.

Affected product: Progressive Robot Ltd hMailServer. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-107575/ (Markdown: https://insights.sbomify.com/CVE-2026-107575/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-107575
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-107575
- OSV: https://osv.dev/vulnerability/CVE-2026-107575

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-107575/
Summaries are generated and may contain mistakes; the official description above is the record.