# CVE-2026-101912: ip-address: isInSubnet() and isHostInSubnet() compare addresses of different families as if they shared an address space, allowing an allowlist check to admit an address outside its range

> Attackers can bypass IP allowlists by exploiting a logic error that incorrectly matches IPv4 and IPv6 addresses, admitting unauthorized access.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** CLEANSTART-2026-EF09079, CLEANSTART-2026-FH34205, CLEANSTART-2026-XD91859, CLEANSTART-2026-XK88053, CLSA-2026-1790854765, CLSA-2026-1790864845, DEBIAN-CVE-2026-101912, ECHO-8502-8e2d-9fce, GHSA-j6r3-76f7-8jcv, MINI-29q3-fccr-889r, MINI-3m4v-wwm6-j97q, MINI-64pp-cj45-mhxj, MINI-6gg9-8fqr-p3qf, MINI-6pfv-xj98-5x98, MINI-7x5f-772m-mcw4, MINI-885h-7g7g-6j9j, MINI-8p8m-hgjv-f3q5, MINI-97h2-5pw2-824v, MINI-9c2x-m65r-r48v, MINI-9f47-6jwh-p2fh, MINI-9rgh-6fm6-g83w, MINI-c7mp-45mm-jmrp, MINI-f3pq-8x4r-jp88, MINI-f5qr-hwm8-39v7, MINI-f994-3ffq-cf9r, MINI-g8mf-pj2m-3h99, MINI-g9gq-66w3-hvf5, MINI-gc22-pq7f-6w9r, MINI-gv6f-7cc7-4jc8, MINI-h8fm-q4rx-jg8q, MINI-mph4-gp25-wh8m, MINI-p7p5-r3rm-p4r2, MINI-r343-gp23-5j8q, MINI-r879-prxr-gf2m, MINI-r879-v837-jgx6, MINI-rg7v-xpf9-w797, MINI-rr43-fvfg-f59f, MINI-vrh5-p628-2rqj, MINI-w3w8-3687-qgw2, MINI-wq6g-fr3p-vxx6, MINI-xcv9-xwg8-q3q6, UBUNTU-CVE-2026-101912

## What is CVE-2026-101912?

CVE-2026-101912 is a medium-severity vulnerability in beaugunderson ip-address, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

ip-address is a library for parsing and manipulating IPv4 and IPv6 addresses in JavaScript. Prior to 10.7.1, the isInSubnet and isHostInSubnet methods in src/common.ts compare masked binary strings without validating that both operands use the same IP family. A cross-family containment check whose leading address bits match makes the masked strings compare equal even though IPv4 and IPv6 do not share an address space. An allowlist or denylist decision can therefore classify an address outside the intended range as contained. This issue is fixed in version 10.7.1.

Weakness: CWE-843 (Access of Resource Using Incompatible Type), CWE-697 (Incorrect Comparison)

## Which versions are affected by CVE-2026-101912?

2 open source packages ship an affected version, including ip-address.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ip-address` | npm | All versions | 10.7.1 |
| `ip-address` | npm | All versions | 10.7.1 |

## How do I fix CVE-2026-101912?

Upgrade ip-address to 10.7.1 or later.

## Is CVE-2026-101912 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101912 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-101912 and fix it if it is affected.

What it is: CVE-2026-101912 is a medium-severity vulnerability in beaugunderson ip-address, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101912 exists.

Affected packages and fixed versions:
- ip-address (npm): affected all versions; fixed in 10.7.1
- ip-address (npm): affected all versions; fixed in 10.7.1

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-2026-101912/ (Markdown: https://insights.sbomify.com/CVE-2026-101912/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-101912
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-101912
- OSV: https://osv.dev/vulnerability/CVE-2026-101912

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-101912/
Summaries are generated and may contain mistakes; the official description above is the record.