Vulnerability in golang (CVE-2026-42501)
Summary
Vulnerability in golang (CVE-2026-42501). Successful exploitation can lead to full system takeover. Mitigation: upgrade to 1.25.10, 1.26.3 or later.
Original description
The description as published by the source.
A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability affects any user using an untrusted module proxy (GOMODPROXY) or checksum database (GOSUMDB). A malicious module proxy can serve altered versions of the Go toolchain. When selecting a different version of the Go toolchain than the currently installed toolchain (due to the GOTOOLCHAIN environment variable, or a go.work or go.mod with a toolchain line), the go command will download and execute a toolchain provided by the module proxy. A malicious module proxy can bypass checksum database validation for this downloaded toolchain. Since this vulnerability affects the security of toolchain downloads, setting GOTOOLCHAIN to a fixed version is not sufficient. You must upgrade your base Go toolchain. The go tool always validates the hash of a toolchain before executing it, so fixed versions will refuse to execute any cached, altered versions of the toolchain. The go tool trusts go.sum files to contain accurate hashes of the current module's dependencies. A malicious proxy exploiting this vulnerability to serve an altered module will have caused an incorrect hash to be recorded in the go.sum. Users who have configured a non-trusted GOPROXY can determine if they have been affected by running "rm go.sum ; go mod tidy ; go mod verify", which will revalidate all dependencies of the current module. The specific flaw in more detail: The go…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-42501 has been found in golang.
Successful exploitation can lead to full system takeover. CVSS score: 7.5/10.
What to do: upgrade golang to 1.25.10, 1.26.3 or later.
If unsure, ask your IT team or search "golang CVE-2026-42501" on the vendor's site.
CVE-2026-42501 (golang) — CWE-347 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated
Patched: 1.25.10, 1.26.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-347) exists in golang.
Check the vendor advisory for the affected versions of golang.
Severity: High (CVSS 7.5/10). Successful exploitation can lead to full system takeover.
Update to 1.25.10, 1.26.3.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'golang' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'golang' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
golangを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade golang to 1.25.10, 1.26.3ステージング環境で 1.25.10, 1.26.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2026-42501 go Fixed in: 1.26.3-r0
- Debian DEBIAN-CVE-2026-42501 golang-1.15
- Ubuntu UBUNTU-CVE-2026-42501 golang-1.10
References
- advisory pkg.go.dev
- patch go.dev
- report go.dev
- web groups.google.com
- web nvd.nist.gov
- web github.com