vulnerability / NVI-00013261 / Revision 2
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
GitHub lists this reviewed advisory for ip-address. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
6.3 MEDIUM (4.0)
security-advisories@github.com severity; no combined Null risk score.
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
ip-address
source listed<= 10.7.0
### Summary `isInSubnet()` and `isHostInSubnet()` accept an address of either family and compare masked binary strings without checking that both operands are the same family. `Address4` pads to 32 bits and `Address6` to 128, so whenever the leading bits agree the strings are equal: `new Address6('a00::1').isInSubnet(new Address4('10.0.0.0/8'))` is `true`, and `new Address4('32.0.0.1').isInSubnet(new Address6('2000::/3'))` is `true`. No IPv4 address is inside an IPv6 network, so both answers are untrue. An application that parses untrusted input as whichever family accepts it and then tests the result against a fixed-family allowlist can admit an address outside the list. ### Details Both methods are in `src/common.ts`: ```ts export function isInSubnet(this: Address4 | Address6, address: Address4 | Address6) { if (this.subnetMask < address.subnetMask) { return false; } return isHostInSubnet.call(this, address); } export function isHostInSubnet(this: Address4 | Address6, address: Address4 | Address6) { return this.mask(address.subnetMask) === address.mask(); } ``` `mask(n)` returns the first `n` bits of the address as a string of `0` and `1`, taken from a represe
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. NIST National Vulnerability Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
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05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-j6r3-76f7-8jcv ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-101912 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Source facts changed; compare the preserved prior revision.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.