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openssl_encrypt EUVDEUVD-2026-60118

| CVE-2026-74901 CRITICAL
Improper Verification of Cryptographic Signature (CWE-347)
2026-08-17 VulnCheck GHSA-jw8h-gwjw-g7rc
Jwt Attack Authentication Bypass Openssl Encrypt
9.3
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
9.3 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
6.5 MEDIUM

Network delivery but requires an active in-transit tampering position (AC:H); core impact is undetected integrity forgery (I:H) with only incidental confidentiality (C:L) and no availability impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
4.0 AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

3
Analysis Generated
Aug 17, 2026 - 13:01 vuln.today
Patch available
Aug 17, 2026 - 12:01 EUVD
CVE Published
Aug 17, 2026 - 11:04 cve.org
CRITICAL 9.3

DescriptionCVE.org

openssl_encrypt versions before 1.4.0 contain an authentication bypass vulnerability in pqc.py where AES-GCM decryption failures trigger fallback to unauthenticated AES-CTR mode. Attackers can modify ciphertext in transit to bypass integrity verification and perform bit-flipping attacks without detection.

AnalysisAI

Authentication bypass in the openssl_encrypt Python library (versions before 1.4.0) lets attackers who can tamper with ciphertext in transit defeat integrity protection, because a failed AES-GCM authenticated decryption in pqc.py silently falls back to unauthenticated AES-CTR. Reported by VulnCheck and carrying a CVSS 4.0 base score of 9.3, the flaw enables undetected bit-flipping and ciphertext manipulation. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Gain in-transit position on ciphertext
Delivery
Capture authenticated AES-GCM message
Exploit
Flip targeted ciphertext bits
Execution
GCM auth fails, falls back to AES-CTR
Persist
Manipulated plaintext accepted as valid
Impact
Message/token integrity forged
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Vulnerability AssessmentAI

Exploitation Exploitation requires that the attacker can modify ciphertext before it is decrypted by openssl_encrypt (an active man-in-the-middle position on the channel, or write access to stored/forwarded ciphertext) and that the target runs a version before 1.4.0 exercising the pqc.py decryption path where the AES-GCM-to-AES-CTR fallback is reachable. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The supplied CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N, VC:H/VI:H/VA:H, score 9.3) rates this critical with a network vector and no privileges or user interaction. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An application uses openssl_encrypt to protect a session token or message that transits an attacker-observable channel. The attacker intercepts the ciphertext, flips targeted bits (e.g., to alter an authorization claim), and forwards it; the vulnerable library's AES-GCM check fails but it falls back to AES-CTR and returns the manipulated plaintext as if valid. …
Remediation Vendor-released patch: 1.4.0 - upgrade openssl_encrypt to version 1.4.0 or later, which removes the insecure AES-CTR fallback so that AES-GCM authentication failures abort decryption instead of silently downgrading. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, inventory all systems and applications using openssl_encrypt library and prioritize those handling sensitive data or customer information. …

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EUVD-2026-60118 vulnerability details – vuln.today
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