CVE-2026-53939Public exploitNetwork attack vector

JWE decryption and forgery via all-zero CEK

Published Sep 8, 2026 · Updated Sep 9, 2026

Cryptographic key generation in OpenIDC cjose 0.6.1 through 0.6.2.5 allows attackers to decrypt and forge affected JWEs. The _cjose_jwe_set_cek_aes_cbc() path in src/jwe.c inverts its random-allocation flag, zero-filling each fresh CEK instead of generating random bytes. Exposure requires AES-CBC-HMAC encryption with a key-management algorithm that asks the library to generate a CEK; anyone obtaining the JWE can read its plaintext and alter authenticated content.

CVSS severity9.1
Critical
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cryptographic key generation in OpenIDC cjose 0.6.1 through 0.6.2.5 allows attackers to decrypt and forge affected JWEs. The _cjose_jwe_set_cek_aes_cbc() path in src/jwe.c inverts its random-allocation flag, zero-filling each fresh CEK instead of generating random bytes. Exposure requires AES-CBC-HMAC encryption with a key-management algorithm that asks the library to generate a CEK; anyone obtaining the JWE can read its plaintext and alter authenticated content.

The record

CVE
CVE-2026-53939
Published
Sep 8, 2026
Updated
Sep 9, 2026
Vendor
OpenIDC
Product
cjose
Classifications
CWE-330, CWE-321, T1140
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 9, 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.

  1. Affected versionversion=>= 0.6.1, < 0.6.2.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenIDC · cjoseversion=>= 0.6.1, < 0.6.2.6

Published CVSS scores

9.1GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-330Use of Insufficiently Random Values
CWE-321Use of Hard-coded Cryptographic Key
T1140Deobfuscate/Decode Files or Information

Public exploit references

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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