Deno's Undead Ciphers: Breaking node:crypto with Infinite Loops
Vulnerability ID: CVE-2026-22863
CVSS Score: 9.2
Published: 2026-01-16
In Deno's quest for Node.js compatibility, a critical flaw in the node:crypto polyfill allowed cryptographic handles to survive past their intended lifespan. By failing to invalidate the internal state after .final(), Deno < 2.6.0 permitted 'infinite encryptions'—allowing attackers to reuse key streams and IVs, completely shattering confidentiality guarantees.
TL;DR
Deno versions prior to 2.6.0 contain a critical logic error in the node:crypto compatibility layer. Calling .final() on a Cipher instance fails to nullify the internal Rust handle. This allows the object to be reused for subsequent encryption operations with the same state, leading to IV reuse and potential plaintext recovery. Update to Deno 2.6.0 immediately.
⚠️ Exploit Status: POC
Technical Details
- CWE: CWE-325 (Missing Cryptographic Step)
- CVSS v4.0: 9.2 (Critical)
- Attack Vector: Network
- Impact: Confidentiality Loss / Keystream Reuse
- Exploit Status: PoC Available
- EPSS Score: 0.00017 (Low Probability)
Affected Systems
- Deno Runtime < 2.6.0
-
Deno: < 2.6.0 (Fixed in:
2.6.0)
Exploit Details
- Internal Research: Proof of Concept demonstrating persistent kHandle after finalization.
Mitigation Strategies
- Upgrade Deno to version 2.6.0 or higher.
- Audit code for reuse of Crypto objects (though this is bad practice generally, this bug makes it fatal).
- Prefer Deno's native Web Crypto API (
crypto.subtle) over thenode:cryptocompatibility layer where possible.
Remediation Steps:
- Check current version:
deno --version - Run upgrade command:
deno upgrade --version 2.6.0 - Restart all Deno processes/services.
References
Read the full report for CVE-2026-22863 on our website for more details including interactive diagrams and full exploit analysis.
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