Vulnerability in nanoid (CVE-2026-73086)
Summary
Vulnerability in nanoid (CVE-2026-73086). Confidential information can be exposed externally. Exploitable via size. Mitigation: upgrade to 5.1.11 or later.
Original description
The description as published by the source.
Summary
An integer overflow in nanoid(size) permanently corrupts the process-wide CSPRNG pool, causing all subsequent ID generation to return the deterministic string "uuuuuuuuuuuuuuuuuuuuu". Any application that passes user-influenced values to the size parameter loses all randomness guarantees for session tokens, CSRF tokens, and unique identifiers until process restart.
Details
nanoid() at index.js:101 coerces the size parameter with size |= 0, which converts it to a signed 32-bit integer. When size >= 2^31 (e.g., 2147483648), this wraps to -2147483648.
The negative value is passed to fillPool() (index.js:15):
function fillPool(bytes) {
if (!pool || pool.length < bytes) { // false: pool exists, -2B < pool.length
pool = Buffer.allocUnsafe(bytes * POOL_SIZE_MULTIPLIER)
crypto.getRandomValues(pool)
poolOffset = 0
} else if (poolOffset + bytes > pool.length) { // false: poolOffset + (-2B) < pool.length
crypto.getRandomValues(pool)
poolOffset = 0
}
poolOffset += bytes // poolOffset += -2147483648 → deeply negative
}
Neither branch triggers, so the pool is never refreshed. poolOffset becomes ~-2.1 billion.
Subsequent nanoid() calls execute:
for (let i = poolOffset - size; i < poolOffset; i++) {
id += scopedUrlAlphabet[pool[i] & 63]
}
`pool[negative_index…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-73086 has been found in nanoid.
Attackers can target a specific entry point like size over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.4/10.
What to do: upgrade nanoid to 5.1.11 or later.
If unsure, ask your IT team or search "nanoid CVE-2026-73086" on the vendor's site.
CVE-2026-73086 (nanoid) — CWE-190 / CVSS v3 7.4
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: size / poolOffset / undefined / nanoid
Patched: 5.1.11 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-190) exists in nanoid. Attackers reach the vulnerable code path via size without authentication.
Check the vendor advisory for the affected versions of nanoid. Attack surface: size / poolOffset / undefined / nanoid.
Severity: High (CVSS 7.4/10). Confidential information can be exposed externally.
Update to 5.1.11.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'nanoid' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'nanoid' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
nanoidを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade nanoid to 5.1.11ステージング環境で 5.1.11 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- ATLASSIAN JSWSERVER-26958
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web nvd.nist.gov
- web github.com