CVE-2026-18536 in Data::Entropy
Summary
by MITRE • 08/01/2026
Data::Entropy versions before 0.010 for Perl read remote entropy sources over plain HTTP.
The Data::Entropy::RawSource::RandomOrg and Data::Entropy::RawSource::RandomnumbersInfo remote sources are accessed over plain HTTP.
The Data::Entropy::RawSource::RandomOrg integrity check trivially matches any non-empty byte string.
Any on-path attacker, such as open WiFi, a compromised ISP, captive portal, or a hostile egress proxy substitutes the response and thereby chooses the bytes returned by rand_bits and rand_int for every application that selected one of these sources via with_entropy_source. The _checkbuf method response is equally attacker-controlled, so the retry/sleep behaviour is steerable too.
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Analysis
by VulDB Data Team • 08/01/2026
The Data::Entropy Perl module presents a critical security vulnerability through its handling of remote entropy sources, specifically affecting versions prior to 0010. This flaw fundamentally compromises the cryptographic security of applications that depend on random number generation, as the module retrieves entropy data from external sources without implementing proper transport security measures. The vulnerability manifests in two primary remote sources: RandomOrg and RandomnumbersInfo, both of which communicate over unencrypted HTTP connections rather than secure HTTPS protocols, creating an attack surface that exposes sensitive cryptographic operations to man-in-the-middle attacks.
The technical implementation of this vulnerability stems from the module's inadequate integrity verification mechanism within the _checkbuf method, which performs a trivial validation that accepts any non-empty byte string as valid. This weak validation allows attackers positioned in the network path between the victim application and the entropy source to substitute legitimate responses with arbitrary data without detection. The attacker's control extends beyond simple data substitution to include manipulation of retry and sleep behaviors through the attacker-controlled response, effectively allowing them to orchestrate timing-based attacks against applications that depend on these entropy sources.
The operational impact of this vulnerability is severe for any application that relies on cryptographically secure random number generation, as it enables attackers to predict or control the output of randomness functions such as rand_bits and rand_int. This compromises the security of cryptographic key generation, session management, authentication tokens, and other security-critical operations that depend on unpredictable entropy. The vulnerability affects applications using with_entropy_source method calls that select either RandomOrg or RandomnumbersInfo sources, potentially allowing attackers to gain unauthorized access to systems, bypass security controls, or perform impersonation attacks.
This vulnerability maps directly to CWE-319: Cleartext Transmission of Sensitive Information and CWE-347: Improper Verification of Cryptographic Signature, as it involves transmitting sensitive cryptographic data over unencrypted channels and fails to properly validate the integrity of remote responses. From an ATT&CK framework perspective, this corresponds to T1566.002: Phishing via Service Provider and T1046: Network Service Scanning, as attackers can exploit the cleartext communication to intercept and manipulate entropy data. The vulnerability also aligns with T1583.001: Acquisition: Web Shell and T1583.002: Acquisition: Software, as compromised systems could be used to host malicious entropy sources or as part of broader attack infrastructure.
Mitigation strategies include upgrading to Data::Entropy version 0.010 or later, which implements proper HTTPS connections and robust integrity checking mechanisms. Organizations should also implement network-level controls such as DNS filtering, certificate pinning, and network segmentation to prevent unauthorized access to entropy sources. Additionally, applications using this module should be reviewed for proper entropy source validation and implementation of fallback mechanisms that do not rely on potentially compromised external sources. The fundamental requirement is to ensure all cryptographic operations use secure transport protocols and implement strong integrity checks that cannot be bypassed by attackers with network access.