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Response snapshot Oct 27, 2026, 06:21 UTC

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VulnerabilityCVE-2026-111997

ip-address: Address6 matches a zone identifier in quadratic time ahead of its length limit, allowing a single long string to stall the process

`new Address6()` and `Address6.isValid()` strip a zone identifier with the pattern `/%.*$/` before they apply the 45-character length limit.

Published Updated

At a glance

Exploited
Not known
Severity
6.3 Medium (CVSS 4.0)
Chance of exploitation
0.3% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: ip-address: 10.7.4. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-rxp7-6hxx-x8q5 (opens a new tab)

What happened

### Summary

`new Address6()` and `Address6.isValid()` strip a zone identifier with the pattern `/%.*$/` before they apply the 45-character length limit. When the string holds many `%` characters followed by a line terminator, the pattern is retried from every `%` and each attempt scans to the line terminator before failing, so rejecting the string takes time proportional to the square of its length.

10,000 `%` characters and a newline take 41 ms, 40,000 take 632 ms and 100,000 take 3.9 s of synchronous work. The same strings without the newline are rejected in under a millisecond.

An application that validates an attacker-supplied string with these methods can be stalled by a single long request. The input is rejected with the correct `AddressError`; the cost of reaching that rejection is the defect.

Continue reading

### Details

The constructor in `src/ipv6.ts` removes the CIDR suffix, then the zone, then checks the length of what is left:

```ts const zone = constants6.RE_ZONE_STRING.exec(address);

if (zone) { this.zone = zone[0];

address = address.replace(constants6.RE_ZONE_STRING, ''); }

const longest = this.groups * 5 + 5;

if (address.length > longest) { throw new AddressError(`IPv6 addresses are at most ${longest} characters.`); } ```

`RE_ZONE_STRING` is `/%.*$/`. It has no anchor at its start, `.` does not match a line terminator (`\n`, `\r`, U+2028 or U+2029), and without the `m` flag `$` matches only at the end of the input. For `%` repeated N times and then `\n`, the engine starts a match at the first `%`, `.*` consumes the remaining `%` characters up to the newline, `$` fails there, and backtracking through every shorter `.*` fails too.

The engine then starts again at the second `%`, and so on: N starts, each proportional to N. The length limit that follows rejects the string in constant time, after the scan has already run.

The line terminator need not be last. Any string in which many `%` characters precede a line terminator behaves the same way.

Every entry point that passes a caller's string to the `Address6` constructor is affected: `new Address6()`, `isValid()`, both arguments of `fromAddressAndMask()` and `fromAddressAndWildcardMask()`, and the prefix argument of `fromAddress4Nat64()` and `toAddress4Nat64()`.

`fromWildcard()` rejects a `%` before it constructs anything, `fromURL()` admits only hex digits, colons and dots in a host, and `fromArpa()` checks the nibble grammar first, so those three are unaffected. `Address4` has no zone and is unaffected.

### Affected versions

` 64) throw new Error('not an IP address'); ```

Affected package ranges reported by GitHub: ip-address: <= 10.7.3

Scores and how they were measured

CVSS base severity

6.3

Version 4.0As of

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.3%

Scored Percentile 24.2%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-rxp7-6hxx-x8q5 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-rxp7-6hxx-x8q5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-111997, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 22). ip-address: Address6 matches a zone identifier in quadratic time ahead of its length limit, allowing a single long string to stall the process (CVE-2026-111997). https://kevwire.com/record/CVE-2026-111997

MLA

"ip-address: Address6 matches a zone identifier in quadratic time ahead of its length limit, allowing a single long string to stall the process (CVE-2026-111997)." KEVWire, 22 Oct. 2026, kevwire.com/record/CVE-2026-111997.

Chicago

KEVWire. "ip-address: Address6 matches a zone identifier in quadratic time ahead of its length limit, allowing a single long string to stall the process (CVE-2026-111997)." Last modified October 22, 2026. https://kevwire.com/record/CVE-2026-111997.

Evidence summary (plain text)

ip-address: Address6 matches a zone identifier in quadratic time ahead of its length limit, allowing a single long string to stall the process (Oct 22, 2026).
`new Address6()` and `Address6.isValid()` strip a zone identifier with the pattern `/%.*$/` before they apply the 45-character length limit. When the string holds many `%` characters followed by a line terminator, the pattern is retried from every `%` and each attempt scans to the line terminator before failing, so rejecting the string takes time proportional to the square of its length. 10,000 `%` characters and a newline take 41 ms, 40,000 take 632 ms and 100,000 take 3.9 s of synchronous work. The same strings without the newline are rejected in under a millisecond.

An application that validates an attacker-supplied string with these methods can be stalled by a single long request. The input is rejected with the correct `AddressError`; the cost of reaching that rejection is the defect.
CVSS 6.3 (version 4.0; evidence as of Oct 22, 2026; https://github.com/advisories/GHSA-rxp7-6hxx-x8q5).
EPSS 0.3% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-111997&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-rxp7-6hxx-x8q5: https://github.com/advisories/GHSA-rxp7-6hxx-x8q5
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo1MTozMFrOAAf0Mg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0OToxMlrOAAf0LQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NzoxN1rOAAf0Kg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTozNlrOAAf0Jw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTowNVrOAAf0JQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0Mzo0NVrOAAf0Iw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0MzozMVrOAAf0Ig%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozNTowMVrOAAZRcw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozMDoyN1rOAAY_5Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODoyOTowNVrOAAfz8g%3D%3D
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-111997&date=2026-10-26
Record ID: CVE-2026-111997.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 01:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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