CVE-2026-81687
Received Received - Intake

OpenSSL Encrypt KDF Iteration Count Denial of Service

Publication date: 2026-08-27

Last updated on: 2026-08-27

Assigner: VulnCheck

Description
openssl_encrypt versions before 1.4.9 fail to enforce a time ceiling on key derivation function iteration counts specified in file metadata. Attackers can craft files with extremely high KDF iteration counts to consume CPU resources for unbounded periods before password verification occurs.

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Meta Information

Published
2026-08-27
Last Modified
2026-08-27
Generated
2026-08-27
AI Q&A
2026-08-27
EPSS Evaluated
N/A
NVD
CVE-2026-81687
EUVD
EUVD-2026-67043

Affected Vendors & Products

Currently, no data is known.

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-400 The product does not properly control the allocation and maintenance of a limited resource.

Attack-Flow Graph

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Executive Summary

This vulnerability affects openssl_encrypt versions before 1.4.9. It allows attackers to craft files with extremely high KDF iteration counts, causing the system to consume excessive CPU resources for extended periods during password verification. The issue stems from a lack of time ceiling enforcement on key derivation function iteration counts in file metadata.

Detection Guidance

Check the installed version of openssl_encrypt with 'openssl_encrypt --version'. If the version is <= 1.4.8, the system is vulnerable. Monitor for unusually high CPU usage during decryption operations, especially with files containing high KDF iteration counts.

Impact Analysis

This vulnerability can lead to denial-of-service (DoS) conditions by consuming CPU resources for impractically long periods. Estimated delays range from 1600 seconds to 4e16 seconds depending on the KDF algorithm. It affects decryption processes, even with flags like --quiet or --no-estimate, and lacks an escape mechanism in unattended decryption scenarios.

Mitigation Strategies

Upgrade openssl_encrypt to version 1.4.9 or later. Avoid processing files from untrusted sources until the update is applied. For temporary mitigation, limit decryption operations to trusted files only.

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