Avoid quadratic complexity when coalescing text nodes in html in golang.org/x/net

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

not scored

EPSS

• CVE-2026-78661: 0.18% estimated exploitation activity in the next 30 days; percentile 8.11 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

When coalescing adjacent text nodes in addText and fosterParent, appending to an existing TextNode's Data via string concatenation (n.Data += text) reallocated and copied the accumulated string on every token. Inputs containing many short text runs separated by ignored end tags (such as "a ") caused O(n^2) allocations and byte copies. Accumulate coalesced text in per-node byte slices during parsing and materialize Data strings once at the end of parse.

Published by the source

27 Oct 2026, 21:16 UTC

Last modified by the source

27 Oct 2026, 21:30 UTC

Source last checked

28 Oct 2026, 06:30 UTC

1. Revision 1 · created · 28 Oct 2026

   Published from osv record GO-2026-6860

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# Patch Next advisory brief: CVE-2026-78661

Advisory: Avoid quadratic complexity when coalescing text nodes in html in golang.org/x/net
IDs: CVE-2026-78661
Record: https://patchnext.com/advisories/cve-2026-78661 (revision 1, source checked 28 Oct 2026, 06:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: golang.org/x/net 0.62.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go golang.org/x/net: affected < 0.62.0; fixed in 0.62.0

## Suggested inspection (read-only)
- Go golang.org/x/net: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on golang.org/x/net.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6860 (OSV record GO-2026-6860 lists affected ranges: Go golang.org/x/net >=0 <0.62.0 (fixed))

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