net/url: quadratic complexity in resolvePath when processing backtrack path elements

[jitsu-net]

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.

This is CVE-2026-56860 and Go issue https://go.dev/issue/80494.

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This was a PUBLIC track issue, tracked in http://b/520476523.

[gopherbot]

Change https://go.dev/cl/803681 mentions this issue: net/url: avoid quadratic complexity in resolvePath

[gabyhelp]

Related Issues

• net/url: improve performance for resolvePath #42180 (closed)
• net/url: JoinPath doesn't strip relative path components in all circumstances #54385 (closed)

Related Code Changes

• net/url: avoid quadratic complexity in resolvePath
• net/url: improve performance for resolvePath
• net/url: avoid string concatenation in resolvePath

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[jitsu-net]

@gopherbot Please open backport for this security issue.

[gopherbot]

Backport issue(s) opened: #80629 (for 1.25), #80630 (for 1.26).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.

[gopherbot]

Change https://go.dev/cl/807560 mentions this issue: [release-branch.go1.25] net/url: avoid quadratic complexity in resolvePath

[gopherbot]

Change https://go.dev/cl/806962 mentions this issue: [release-branch.go1.26] net/url: avoid quadratic complexity in resolvePath

[gopherbot]

Change https://go.dev/cl/807700 mentions this issue: [release-branch.go1.27] net/url: avoid quadratic complexity in resolvePath