Net::BitTorrent versions through 2.0.1 for Perl generate the MSE Diffie-Hellman private key with a non-cryptographic PRNG

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Summary

CVECVE-2026-57082
StatePUBLISHED
AssignerCPANSec
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-30 12:16:25 UTC
Updated2026-06-30 15:16:58 UTC
DescriptionNet::BitTorrent versions through 2.0.1 for Perl generate the MSE Diffie-Hellman private key with a non-cryptographic PRNG. The MSE (Message Stream Encryption) handshake derives its 160-bit Diffie-Hellman private key from Perl's rand(), a non-cryptographic drand48-class generator seeded once per process, in KeyExchange.pm. The shared secret and the RC4 keys derived from it (the SHA-1 of "keyA" or "keyB", the shared secret, and the infohash) therefore depend entirely on a predictable PRNG. The same handshake sends, in cleartext, random padding drawn from the same rand() sequence in _random_pad, immediately after the public key and the private-key draw. A passive observer of the handshake recovers the PRNG state from the cleartext padding, reconstructs the private key, computes the shared secret from the peer's public key on the wire, derives the RC4 keys, and decrypts the connection, defeating the passive-observation obfuscation MSE provides.

Risk And Classification

Primary CVSS: v3.1 5.9 MEDIUM from ADP

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Problem Types: CWE-330 | CWE-338 | CWE-338 CWE-338 Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) | CWE-330 CWE-330 Use of Insufficiently Random Values

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA SANKO NetBitTorrent affected 2.0.1 custom Not specified

References

ReferenceSourceLinkTags
github.com/sanko/Net-BitTorrent.pm/security/advisories/GHSA-g444-x2c5-94hc 9b29abf9-4ab0-4765-b253-1875cd9b441e github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

Workarounds

CNA: There is no fixed release. Draw the Diffie-Hellman private key and the handshake padding from a cryptographic source such as Crypt::URandom rather than rand().

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