EUVD-2026-38542Published

Deno: WebSocket API sandbox bypass via missing post-DNS check

Collected exploitation and prediction evidence

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2026-49860

Published

Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, 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. This vulnerability is fixed in 2.8.1.

Source published: 23 Jun 2026 17:15:05 UTC
Source modified: 23 Jun 2026 17:37:07 UTC
Observed here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

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CVSS 3.1 · 5.2 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

euvd · EUVD-2026-38542

Published

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Jun 23, 2026, 5:15:05 PM

dateUpdated: Jun 23, 2026, 5:37:07 PM

Source published: Jun 23, 2026, 5:15:05 PM (timezone not stated)
Source modified: Jun 23, 2026, 5:37:07 PM (timezone not stated)
Observed here: 7 Nov 2026 11:32:15 UTC
Source terms: ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 5.2 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

nvd · CVE-2026-49860

Published

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-918

Original publisher date fields

published: 2026-06-23T18:18:04.053

lastModified: 2026-10-25T23:10:00.167

1 source CPE criteria · context only

cpe:2.3:a:deno:deno:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Source published: 23 Jun 2026 18:18:04 UTC
Source modified: 25 Oct 2026 23:10:00 UTC
Observed here: 27 Oct 2026 13:11:58 UTC
Source terms: NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 5.2 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

osv · GHSA-83pc-3rw9-qpwj

Published

## 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-net` to 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 published: 16 Jun 2026 19:04:07 UTC
Source modified: 20 Jul 2026 21:15:27 UTC
Observed here: 24 Oct 2026 13:19:54 UTC
Source terms: GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

Publisher rating · MODERATE