Vulnerability in deno (CVE-2026-49859)
Summary
Vulnerability in deno (CVE-2026-49859). Risk of unauthorized operations or information disclosure. Exploitable via localhost. Mitigation: upgrade to 2.8.1 or later.
Original description
The description as published by the source.
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, when fetch() was called, Deno checked the destination hostname against --deny-net rules but did not re-check the IP addresses that hostname resolved to. An attacker-controlled script could use a specially crafted domain name that passes the hostname check yet resolves to a denied IP, bypassing the network restriction entirely. This vulnerability is fixed in 2.8.1.
Source: GitHub Security Advisories (Global) 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-2026-49859 has been found in deno.
Attackers can target a specific entry point like localhost over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.2/10.
What to do: upgrade deno to 2.8.1 or later.
If unsure, ask your IT team or search "deno CVE-2026-49859" on the vendor's site.
CVE-2026-49859 (deno) — CWE-693 / CVSS v3 5.2
Attack vector: local / no user interaction
Attack surface: localhost / Deno.connect
Patched: 2.8.1 — 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-693) exists in deno. Attackers reach the vulnerable code path via localhost.
Check the vendor advisory for the affected versions of deno. Attack surface: localhost / Deno.connect.
Severity: Medium (CVSS 5.2/10). Risk of unauthorized operations or information disclosure.
Update to 2.8.1.
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 'deno' . 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 'deno' . | 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
deno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 deno to 2.8.1ステージング環境で 2.8.1 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
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- web github.com