Token prediction via signed size wraparound
Published Aug 11, 2026 · Updated Aug 11, 2026
Integer overflow in Evil Martians Nano ID before 3.3.12 and 4.0.0 through 5.1.10 allows remote attackers to predict generated tokens. The nanoid(size) path coerces an external size to signed 32-bit, passes the wrapped negative value to fillPool(), and drives poolOffset below zero so later byte reads resolve to a constant alphabet index. Reachability requires an application to pass attacker-controlled size values; one request then makes later session tokens, CSRF tokens, API keys, and identifiers identical until the process restarts.
Summary
What happened
Integer overflow in Evil Martians Nano ID before 3.3.12 and 4.0.0 through 5.1.10 allows remote attackers to predict generated tokens. The nanoid(size) path coerces an external size to signed 32-bit, passes the wrapped negative value to fillPool(), and drives poolOffset below zero so later byte reads resolve to a constant alphabet index. Reachability requires an application to pass attacker-controlled size values; one request then makes later session tokens, CSRF tokens, API keys, and identifiers identical until the process restarts.
The record
- CVE
- CVE-2026-73086
- Published
- Aug 11, 2026
- Updated
- Aug 11, 2026
- Vendor
- Evil Martians
- Product
- Nano ID
- Classifications
- CWE-190, T1550.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 11, 2026CVE publishedPublication date reported by the CVE source.
- Aug 11, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 3.3.12
- Affected versionversion=>= 4.0.0, < 5.1.11
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA nanoid size-wraparound proof of conceptproof of concept · unverified
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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