How severe is CVE-2026-49983?

CVE-2026-49983 has a CVSS 3.x base score of 5.2, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-49983 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (1st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-49983?

CVE-2026-49983 affects Deno. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-49983?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-49983 have an EU (EUVD) identifier?

Yes. CVE-2026-49983 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38543.

When was CVE-2026-49983 published?

CVE-2026-49983 was published on 2026-06-23 and last updated on 2026-06-29.

CVE-2026-49983

CVE-2026-49983 is a medium-severity vulnerability in Deno with a CVSS 3.x base score of 5.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-863.

Key facts

Severity: Medium (CVSS 3.x base score 5.2)
EPSS exploit prediction: 0% (1st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38543
Weakness: CWE-863
Affected product: Deno
Published: 2026-06-23
Last modified: 2026-06-29

Description

Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, environment access is gated by the env permission. You can deny it with --deny-env, or restrict it to a specific allowlist with --allow-env=FOO,BAR. The expectation is that a program running without env permission cannot change process.env. process.loadEnvFile() (the Node-compatible API for loading variables from a .env file) does not honor this. It only checks that the program has read permission for the dotenv file, then writes every key in that file into the process environment — even when env access is denied. In effect, --allow-read plus a writable or attacker-controlled .env file is enough to defeat --deny-env. This vulnerability is fixed in 2.8.1.

Frequently asked questions

What is CVE-2026-49983?: Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, environment access is gated by the env permission. You can deny it with --deny-env, or restrict it to a specific allowlist with --allow-env=FOO,BAR. The expectation is that a program running without env permission cannot change process.env. process.loadEnvFile() (the Node-compatible API for loading variables from a .env file) does not honor this. It only checks that the program has read permission for the dotenv file, then writes every key in that file into the process environment — even when env access is denied. In effect, --allow-read plus a writable or attacker-controlled .env file is enough to defeat --deny-env. This vulnerability is fixed in 2.8.1.
How severe is CVE-2026-49983?: CVE-2026-49983 has a CVSS 3.x base score of 5.2, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-49983 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (1st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-49983?: CVE-2026-49983 affects Deno. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-49983?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-49983 have an EU (EUVD) identifier?: Yes. CVE-2026-49983 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38543.
When was CVE-2026-49983 published?: CVE-2026-49983 was published on 2026-06-23 and last updated on 2026-06-29.

References

https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv

Affected products (1)

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

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