Cyber Resilience

CVE-2021-44521

RCE in Apache Cassandra 3.0.0 – 3.0.26

Public PoCHigh EPSSRCE
Published
11 February 2022
Modified
21 November 2024
Patch / advisory
CVSS Score v3.1 9.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
EPSS Score 0.55 99th percentile
Risk Priority 80 floored blend · peak EPSS

Summary

CVE-2021-44521 is a critical-severity Code Injection (CWE-94) vulnerability in Apache Cassandra. Its CVSS base score is 9.1 (Critical).

Operationally, ranked in the top 1% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

When running Apache Cassandra with the following configuration: enable_user_defined_functions: true enable_scripted_user_defined_functions: true enable_user_defined_functions_threads: false it is possible for an attacker to execute arbitrary code on the host. The attacker would need to have enough permissions to create user defined functions…

more

in the cluster to be able to exploit this. Note that this configuration is documented as unsafe, and will continue to be considered unsafe after this CVE.

CWE(s)

Related Threats

Likely ATT&CK TechniquesAI

Techniques this vulnerability likely enables, inferred from its description, weakness type, and attributed-actor tradecraft. Confidence is per-technique.

T1059 Command and Scripting Interpreter Executionconfidence: HIGH
UDF execution with scripted UDFs and threading disabled allows direct arbitrary code execution on the host.
T1068 Exploitation for Privilege Escalation Privilege Escalationconfidence: HIGH
Successful exploitation of the unsafe UDF configuration grants code execution, enabling privilege escalation on the Cassandra node.
inferred from description + CWE · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2023-28706Same vendor: Apache
CVE-2024-51941Same vendor: Apache
CVE-2024-36268Same vendor: Apache
CVE-2023-51387Same vendor: Apache
CVE-2023-50379Same vendor: Apache
CVE-2025-59302Same vendor: Apache
CVE-2013-2115Same vendor: Apache
CVE-2026-25077Same vendor: Apache
CVE-2025-54550Same vendor: Apache
CVE-2025-27446Same vendor: Apache

Affected Assets

apache
cassandra
3.0.0 — 3.0.26 · 3.11.0 — 3.11.12 · 4.0.0 — 4.0.2

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

Detect
Catch it (NIST detect / respond)

Harden
Shrink the surface (DISA STIG)
  • 7 hardening rules · 4 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V1.3.1

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-732 CWE-94

Overrides or renders irrelevant incorrect permission assignments on critical executable resources by using hardware-level immutability.

addresses: CWE-732

Procedures support proper permission assignment for critical resources through documented controls.

addresses: CWE-732

Attribute management for resources provides a mechanism to assign and maintain correct permissions based on security labels.

addresses: CWE-732

Prevents overly permissive assignments to critical resources by limiting to task needs.

addresses: CWE-732

Training policy covers correct permission assignment, reducing the ability to exploit incorrect permission assignments for critical resources.

addresses: CWE-732

Training on permission management reduces incorrect permission assignments for critical resources.

addresses: CWE-732

Audit logs and logging tools are critical resources whose protection requires correct permission assignments to block unauthorized actions.

addresses: CWE-732

Assessments review permission assignments on critical resources to confirm correctness, mitigating exploitation via incorrect permissions.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-05 full match
prevents

Directly requires defining, enforcing, and reviewing access permissions and least privilege on resources.

PR.PS-01 mostly match
prevents

Hardened baselines and configuration management explicitly include correct permission settings for critical resources.

PR.PS-06 mostly match
prevents

PR.PS-06's SDLC practices directly target injection flaws via secure coding and testing (mostly), yet as a single broad outcome it leaves many code-generation specifics unaddressed (partial).

PR.DS-10 none match
prevents

PR.DS-10 protects runtime data confidentiality/integrity but has no bearing on neutralizing externally influenced input during code generation, so neither direction shows any preventive effect.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

prevents

By requiring owners to determine and document the exact permissions needed for each asset, the control reduces the likelihood that default or overly permissive file and resource permissions will be left in place.

prevents

Documented provisioning and revocation procedures reduce the chance that critical resources retain overly permissive default or leftover permissions after personnel changes.

prevents

Documented authorization, expiry rules, and audit logging of privileged accounts make it harder for critical resources to retain overly permissive or stale permission assignments.

prevents

Requiring explicit configuration of access controls and permissions for files, applications and services counters the assignment of overly permissive default or incorrect file-system rights.

prevents

Enforcing differentiated permissions on the source-code repository and program listings stops the assignment of overly broad default or inherited permissions to critical resources.

prevents

By defining and enforcing secure permission settings in configuration templates, the control reduces the likelihood that critical resources receive incorrect permission assignments.

References