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HighVulnerabilityCVE-2026-119283updated 30 Oct 2026, 14:55 UTC

joserfc JWE decryption can be made to use excessive CPU

An attacker can send one small request containing many fake recipients, forcing the server to do heavy private-key math for each one. Enough of these requests can slow or freeze the service.

Fixed in joserfc 1.7.5 · out Official, 2 sources
SeverityHighCVSS 7.5 of 10
Being exploited?UnclearNo reports either way yet
Fix available?Yesjoserfc 1.7.5 · since 30 Oct 2026
How sure is this?Official, 2 sourcesBacked by an official source

How the attack works simplified

  1. 1Attacker sends JWESmall request with many fake recipients
  2. 2App calls decrypt_jsonParses every recipient entry
  3. 3RSA decrypt per recipientPrivate-key operation repeated for each entry
  4. 4CPU exhaustedRepeated requests slow or stall the service
  5. ResultService becomes unavailable from CPU exhaustion

What happened

joserfc.jwe.decrypt_json() processes every entry in the JWE General JSON 'recipients' array with no count limit, calling decrypt_cek() (an RSA private-key operation for RSA key-management algorithms) once per entry. The verify_all_recipients option does not prevent this work.

Why it is dangerous: Attacker-controlled request size translates almost 1:1 into server CPU time, enabling denial of service against any endpoint that decrypts JWE JSON with an RSA key, such as RSA-OAEP. Confidentiality and integrity are not affected.

Are you affected?

You are affected if you use the joserfc Python library before 1.7.5 to decrypt JWE General JSON Serialization input with RSA key-management algorithms on an endpoint reachable by untrusted users.

Package / productAffected versionsFixed in
joserfc · pip< 1.7.51.7.5

What to do

  1. Upgrade joserfc to 1.7.5 or later (pip install --upgrade joserfc)
  2. Verify the installed version with pip show joserfc
  3. If you cannot upgrade, limit request body size and rate-limit endpoints that decrypt untrusted JWE JSON

Timeline

  1. 29 Oct 2026, 22:17 UTC
    Publicly disclosed
  2. 29 Oct 2026, 22:17 UTC
    Reported by NVD · NVD
  3. 29 Oct 2026, 22:17 UTC
    Picked up by Zero Radar
  4. 30 Oct 2026, 14:55 UTC
    GitHub Advisory reported on it · GitHub Advisory
  5. 30 Oct 2026, 14:55 UTC
    Fixed version published: joserfc 1.7.5 · GitHub Advisory

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-119283 · GHSA-jpxq-7h8p-2q76
CVSS
7.5 / 10
Disclosed
29 Oct 2026, 22:17 UTC
On Zero Radar
29 Oct 2026, 22:17 UTC (0 min after disclosure)
Last change
30 Oct 2026, 14:55 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

joserfc JWE decryption can be made to use excessive CPU · Zero Radar