Live Exposure Defense: From CVE to Confirmed Exposure in 12 Hours – See more

Back
New CVE Detected

CVE-2026-53938 – Heap Buffer Overflow / Pre-Auth DoS – cjose ≤ 0.6.2.4

Be the first to know when new zero-days emerge:

Subscribe to Email Alerts
Subscribe to RSS Feed

Summary

CVE-2026-53938 is a heap buffer overflow vulnerability in cjose, a C library implementing the JOSE (JSON Object Signing and Encryption) standard, affecting its JWE (JSON Web Encryption) decryption logic for AES Key Wrap algorithms. The library fails to validate the length of an attacker-supplied encrypted key before unwrapping it into a fixed-size heap buffer, allowing a remote, unauthenticated attacker to trigger out-of-bounds heap writes by submitting a crafted JWE token. The flaw carries a CVSS v3.1 base score of 8.2 (High) and can result in denial of service and potential memory corruption.

Technical details

  • Root cause: The _cjose_jwe_decrypt_ek_aes_kw() function in src/jwe.c does not verify that the encrypted key (enc_key) length matches the expected size (CEK length + 8 bytes, per RFC 3394) before passing it to OpenSSL’s AES_unwrap_key().
  • Trigger conditions: An attacker crafts a JWE token with an encrypted key field longer than expected for the AES Key Wrap algorithm in use (A128KW, A192KW, or A256KW) and submits it to any application that decrypts JWEs using cjose.
  • Attack vector: Network (AV:N) — no authentication or user interaction is required; any service that accepts and decrypts attacker-supplied JWE tokens is exposed.
  • Impact: AES_unwrap_key() writes attacker-controlled amounts of data into a fixed-size CEK (Content Encryption Key) buffer, corrupting heap memory. This can crash the decrypting process (denial of service) and, depending on heap layout and allocator behavior, may lead to further memory corruption.
  • Weakness classifications: CWE-122 (Heap-based Buffer Overflow), CWE-787 (Out-of-bounds Write).

Affected software

  • OpenIDC/cjose versions up to and including 0.6.2.4
  • Any application or service embedding an affected cjose version to perform JWE decryption using AES Key Wrap algorithms (A128KW, A192KW, A256KW)

Severity

  • CVSS v3.1 Base Score: 8.2 (High)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Mitigation and recommended actions

  • Immediate: Upgrade cjose to version 0.6.2.5 or later, which adds explicit validation that the encrypted key length equals the expected CEK length plus 8 bytes before invoking the AES unwrap routine.
  • If no patch can be applied immediately:
    • Restrict or disable JWE decryption paths that accept AES Key Wrap (A128KW/A192KW/A256KW) protected tokens from untrusted or external sources until patched.
    • Deploy network-layer controls (WAF/API gateway rules) to filter malformed or abnormally large JWE payloads reaching services that use cjose.
    • Monitor for crashes/segfaults in services using cjose as a potential indicator of exploitation attempts.
    • Rebuild and redeploy any statically linked binaries or containers that bundle a vulnerable cjose version.

References

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report

How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report
Close

Subscribe to Threat Center RSS

Copy/paste the link below into your preferred RSS reader or follow these instructions to subscribe to Slack alerts.

Open RSS feedSlack setup instructions

Close

Get Real-Time CVE Alerts to Your Email

Be the first to know when new zero-days emerge