Vulnerability in Deno
CVE-2026-49440
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 product of two primes just above it, such as 17,881 × 17,891 — was reported as true ("probably prime"). The same divergence affected the lower-level op_node_check_prime / op_node_check_prime_bytes paths that the polyfill calls into. This vulnerability is fixed in 2.8.1.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.002 (13.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 13th percentile — 13.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- Deno
- Denoland Deno — versions < 2.8.1
Weakness classification (CWE)
References
- github.com/denoland/deno/security/advisories/GHSA-9xg4-qhm4-g43w (Third Party Advisory)
- github.com/denoland/deno/pull/34391 (Issue Tracking)
Frequently asked questions
- What is CVE-2026-49440?
- CVE-2026-49440 is a high-severity vulnerability in Deno, classified under Missing Cryptographic Step. CVSS score: 7.4/10. Published 2026-06-23.
- How severe is CVE-2026-49440?
- High severity. CVSS v3 base score is 7.4 out of 10.