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CWE-330Weakness · CWE-330

CVE-2026-57082

MEDIUM · 5.9 CVSS v3.1 Published 2026-06-30
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click 8 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Net::BitTorrent versions before 2.1.0 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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Net::BitTorrent versions before 2.1.0 use Perl's non-cryptographic rand() function to generate 160-bit Diffie-Hellman private keys during the MSE handshake. Since the same PRNG also generates cleartext padding sent immediately after the public key, a passive observer can recover the PRNG state from that padding, reconstruct the private key, derive the RC4 keys, and decrypt the entire encrypted stream.

MitigationUpgrade to Net::BitTorrent version 2.1.0 or later, which replaces the non-cryptographic rand() with a proper cryptographic PRNG for key generation and padding.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm Net::BitTorrent installation and version
    Run 'perl -MNet::BitTorrent -e "print $Net::BitTorrent::VERSION"' to retrieve the installed version number
    Affected if The library is installed and version cannot be verified as patched against this issue
  2. Identify if MSE encryption is enabled
    Inspect the BitTorrent client configuration or application settings that uses Net::BitTorrent; look for settings related to MSE, 'Protocol Encryption', or 'Outgoing/Incoming connections' set to 'Encrypted'
    Affected if MSE or protocol encryption is enabled in the configuration, as the vulnerability only applies to MSE-protected connections
  3. Verify MSE handshake is in use
    Capture network traffic using a packet sniffer (tcpdump, Wireshark) and observe BitTorrent protocol messages for the MSE handshake exchange; look for the cleartext padding bytes immediately following the public key
    Affected if MSE-encrypted peer connections are actively used, exposing the cleartext padding that leaks PRNG state
  4. Compare installed version to any patched releases
    Check the Net::BitTorrent release notes, CPAN metadata, or project repository for version information and compare against any available patched versions addressing this issue
    Affected if The installed version predates any available patch that replaces rand() with a CSPRNG

A system is affected if Net::BitTorrent is installed with MSE/protocol encryption enabled and the library version uses Perl's rand() for Diffie-Hellman private key generation during the MSE handshake.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Net::BitTorrent version 2.1.0 or later, which replaces the non-cryptographic rand() with a proper cryptographic PRNG for key generation and padding.

Recommended fix High confidence

2.1.0

  1. Upgrade Net::BitTorrent Perl module to version 2.1.0 or later via CPAN: `cpan -i Net::BitTorrent` or `cpanm Net::BitTorrent`
  2. Verify the installed version matches or exceeds 2.1.0 using `perl -MNet::BitTorrent -e 'print $Net::BitTorrent::VERSION'
  3. If using Net::BitTorrent in existing code, test that MSE-encrypted BitTorrent connections still function correctly after the upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-57082 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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