# CVE-2026-112991: MISP html_to_markdown Module SSRF via Incomplete IP Range Blocking in is_safe_url()

> An authenticated user can exploit incomplete IP blocking in MISP Modules to perform server-side request forgery and read data from internal network services.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Oct 2026
- **Updated:** 20 Oct 2026
- **Also known as:** GHSA-x7r8-hgm5-qq32

## What is CVE-2026-112991?

CVE-2026-112991 is a medium-severity server-side request forgery vulnerability in misp-modules, published on 19 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The html_to_markdown expansion module in MISP Modules contains a server-side request forgery (SSRF) vulnerability in its is_safe_url() URL validation function. The BLOCKED_RANGES list used to reject unsafe destination addresses was incomplete, omitting several critical IP address ranges. Specifically, the following ranges were not blocked: 0.0.0.0/8 (unspecified, which routes to loopback on Linux), 100.64.0.0/10 (carrier-grade NAT per RFC 6598), ::/128 (IPv6 unspecified), fc00::/7 (IPv6 Unique Local Addresses), and fe80::/10 (IPv6 link-local). The existing list only covered IPv4 loopback (127.0.0.0/8), RFC 1918 private ranges, IPv4 link-local (169.254.0.0/16), and IPv6 loopback (::1/128).

An authenticated user with the ability to create or modify MISP attributes that trigger the html_to_markdown expansion module could supply URLs pointing to these unblocked internal address ranges. Because the module fetches the URL server-side to convert HTML content to Markdown, the request is made from the MISP server's network context. This allows an attacker to probe and read responses from internal services, carrier-grade NAT infrastructure, or link-local endpoints that would otherwise be unreachable from external networks. IPv4-mapped IPv6 forms (e.g., [::ffff:0.0.0.0]) also bypassed the existing checks.

The security impact is primarily confidentiality: an attacker can read data served by internal services reachable from the MISP server. The MISP instance itself is not compromised, but it is abused as a proxy to access otherwise restricted network resources.

Weakness: CWE-918 (Server-Side Request Forgery), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-112991?


## How do I fix CVE-2026-112991?

No fix has been published for CVE-2026-112991 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-112991 being exploited?

There is no known exploitation of CVE-2026-112991 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-112991 and fix it if it is affected.

What it is: CVE-2026-112991 is a medium-severity server-side request forgery vulnerability in misp-modules, published on 19 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-112991 in the wild and no public exploit code.

Affected product: misp-modules. 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-2026-112991/ (Markdown: https://insights.sbomify.com/CVE-2026-112991/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-112991
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-112991
- OSV: https://osv.dev/vulnerability/CVE-2026-112991

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-112991/
Summaries are generated and may contain mistakes; the official description above is the record.