SSRF (Server-Side Request Forgery) in deno (CVE-2026-49860)
Summary
SSRF in deno (CVE-2026-49860). 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.
Summary
When a WebSocket connection was opened, 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.
Impact
Code running under --deny-net could connect to hosts that the user intended
to block. In practice this means network isolation rules — for example,
blocking access to localhost or internal services — could be silently
circumvented by a malicious or compromised dependency.
Deno.connect and fetch() were not affected by this specific issue (a
companion advisory covers fetch()).
Who is affected
Users who:
- run untrusted or third-party code with
deno run, and - rely on
--deny-netto restrict which hosts that code can reach.
If you do not use --deny-net, or if you only run fully trusted code, you are
not affected.
Workaround
No workaround is available short of upgrading. If upgrading immediately is not
possible, avoid granting --allow-net to untrusted code that also has
--deny-net restrictions you depend on for security.
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-2026-49860 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-2026-49860" on the vendor's site.
CVE-2026-49860 (deno) — CWE-918 / 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.
SSRF (CWE-918) 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
-
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。
-
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 nvd.nist.gov
- package github.com
- web github.com
- web github.com