Exploited: 178
LatestCVE-2026-115732 — Certificate Name Authorization Bypass
VulnFeed.org
AREN
7.5
CVE-2026-119283Fix available

joserfc: Unbounded JWE General JSON `recipients` Array Leads to CPU Exhaustion (DoS) via Repeated RSA Private-Key Decryption

joserfc2 min readRead in
AREN

Summary

### Summary `joserfc.jwe.decrypt_json()`, the library's public parser for JWE General JSON Serialization, accepts an attacker-controlled `recipients` array of unbounded length and performs one full private-key decryption operation (`decrypt_cek`) for **every** recipient present in the input, with no cap on recipient count. An unauthenticated network attacker who can send a JWE General JSON document to any endpoint that decrypts it with an RSA key (e.g. RSA-OAEP) can force the victim to perform an arbitrary, attacker-chosen number of RSA private-key decryption operations from a single, relatively small HTTP request. This gives the attacker a highly asymmetric CPU-exhaustion (Denial of Service) primitive: local reproduction shows request size growing linearly with recipient count (~396 bytes/recipient) while server-side CPU time grows in lock-step (near 1:1 ratio between recipient-count growth and decrypt-time growth), and the library's only documented mitigation knob, `verify_all_recipients=False`, does **not** reduce the CPU cost, since the decrypt loop attempts every recipient's `decrypt_cek()` unconditionally before that flag is ever consulted. This is CWE-400 (Uncontrolled Resource Consumption) with CVSS v3.1 Base Score 7.5 (High). ### Details `joserfc` validates and caps several structural elements of a JWE (protected header size, encrypted key size, IV size, ciphertext size, and auth-tag size) inside `src/joserfc/_rfc7516/registry.py`, but performs **no validation whatsoever on the number of entries in the `recipients` array** of a JWE General JSON Serialization object. Data flow (source → sink), verified directly against the repository source at commit `26a10275e88276184f91ae2a6409647bfac7fea5` (joserfc 1.7.4): 1. `src/joserfc/jwe.py:214` — public parser entry point `decrypt_json(data, private_key, ...)`. This is a documented, unauthenticated (at the library boundary) API for parsing externally supplied JWE JSON. 2. `src/joserfc/jwe.py:238` — if `"recipients"…

Remediation

References

Esc