CVE-2026-81717: openssl_encrypt before 1.4.9 Integrity Bypass via Added Files
opensslencrypt (pip package openssl-encrypt) before 1.4.9 contains two weaknesses in the portable USB drive feature, whose threat model treats the removable drive as untrusted (attacker with physical write access). USBDriveCreator.verifyintegrityfile only validates files listed in the manifest, so files added to the drive — including a root-level autorun payload — are not detected and integrity verification still passes. Additionally, a globally constant, source-embedded KDF salt (LEGACYFIXEDSALT) is used to derive the drive encryption key for any drive lacking a per-drive salt file, defeating precomputation resistance and enabling an offline rainbow-table attack.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
openssl_encrypt (pip package openssl-encrypt)to a version that resolves this vulnerability.Fixed in 1.4.9 - Compensating control
Treat the removable USB drive as untrusted (attacker with physical write access) and add external controls accordingly to mitigate integrity bypass via added files (e.g., prevent/monitor execution of autorun-style payloads from the drive).
Event History
Frequently Asked Questions
Who is realistically exposed to this issue?
Users of the portable USB drive feature are exposed when an attacker can physically write to the removable drive. The integrity-check weakness allows attacker-added files, including a root-level autorun payload, to remain undetected while verification passes.
What is required to exploit the encryption-key weakness?
The affected drive must lack a per-drive salt file. In that case, the software derives its encryption key using a globally constant salt embedded in the source, enabling offline rainbow-table attacks rather than per-drive precomputation resistance.
How can I determine whether a drive is affected by the weaker key derivation?
Check whether the portable drive has a per-drive salt file. Drives without one use the legacy globally fixed salt described in the advisory.
What version should be used to address these weaknesses?
The issue affects openssl-encrypt versions before 1.4.9. Upgrade to version 1.4.9 or later.