CVE-2026-49440: Deno is a JavaScript, TypeScript, and WebAssembly runtime

Q: How do I fix CVE-2026-49440?

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

Q: Is CVE-2026-49440 being exploited?

CVE-2026-49440 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-49440 affect?

CVE-2026-49440 affects deno. Severity is high (CVSS 7.4). Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, node:crypto.checkPrime(candidate[, options][, callback]) and crypto.checkPrimeSync(candidate[, options]) ran no Miller-Rabin rounds at all when the caller left optio

Q: How urgent is CVE-2026-49440?

Priority 35/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.4REMOTEUPGRADE

CVE-2026-49440 is a high-severity flaw (CVSS 7.4) 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, node:crypto.checkPrime(candidate[, options][, callback]) and crypto.checkPrimeSync(candidate[, options]) ran no Miller-Rabin rounds at all when the caller left options.checks at its default of 0. In that mode, the only test applied to the candidate was trial division by the primes up to 17,863. Any composite whose smallest prime factor exceeds that bound — for example the

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.4 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 85%)
CISA exploited list	No
Weakness	CWE-325
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: < 2.8.1

Fixed in: 2.8.1

Safe to downgrade to: no unaffected older release

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.

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-2026-49440?

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

Is CVE-2026-49440 being exploited?

CVE-2026-49440 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-2026-49440 affect?

CVE-2026-49440 affects deno. Severity is high (CVSS 7.4). Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, node:crypto.checkPrime(candidate[, options][, callback]) and crypto.checkPrimeSync(candidate[, options]) ran no Miller-Rabin rounds at all when the caller left optio

How urgent is CVE-2026-49440?

Priority 35/100. High severity; Remotely exploitable, no login, no user action

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-2026-49401 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
CVE-2026-49406 MEDIUM 5.5 UPGRADE Deno is a JavaScript, TypeScript, and WebAssembly runtime

References

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