CVE-2026-49983: Deno is a JavaScript, TypeScript, and WebAssembly runtime

Routine

MEDIUM 5.2UPGRADE

CVE-2026-49983 is a medium-severity flaw (CVSS 5.2) affecting deno. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 pr

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.2 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.1% (top 97%)
CISA exploited list	No
Weakness	CWE-863
Published	2026-06-23
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: deno

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-23 18:18 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

deno deno UPGRADE

Affected: >= 2.3.0 and < 2.8.1

Fixed in: 2.8.1

Safe to downgrade to: a release before 2.3.0

1. Check installed version

apt-cache policy deno || rpm -q deno || deno --version

2. UPGRADE to 2.8.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade deno

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade deno

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.3.0 (Debian / Ubuntu)

apt-cache madison deno sudo apt install deno=<VERSION_BEFORE_2.3.0> sudo apt-mark hold deno

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list deno sudo dnf downgrade deno-<VERSION_BEFORE_2.3.0> sudo dnf versionlock add deno

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-49983?

deno: upgrade to 2.8.1. Exact commands for each OS are on this page.

Is CVE-2026-49983 being exploited?

CVE-2026-49983 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-49983 affect?

CVE-2026-49983 affects deno. Severity is medium (CVSS 5.2). 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

How urgent is CVE-2026-49983?

Priority 19/100. No elevated risk signals yet.

Related CVEs

CVE-2026-49402 HIGH 8.1 UPGRADE Deno is a JavaScript, TypeScript, and WebAssembly runtime
CVE-2026-44726 HIGH 7.4 UPGRADE Deno is a JavaScript, TypeScript, and WebAssembly runtime
CVE-2026-49440 HIGH 7.4 UPGRADE Deno is a JavaScript, TypeScript, and WebAssembly runtime
CVE-2026-49401 HIGH 7.3 UPGRADE Deno is a JavaScript, TypeScript, and WebAssembly runtime
CVE-2026-49411 MEDIUM 6.5 UPGRADE Deno is a JavaScript, TypeScript, and WebAssembly runtime

References

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