Risk Letters

Exploited vulnerability

CVE-2026-117601

TLP:CLEAR

electrum electrum Improper Verification of Cryptographic Signature

Electrum before 4.8.3 fails to verify signatures of wallet-owned inputs in unconfirmed mempool transactions, allowing malicious servers to replace a just-broadcast transaction with a conflicting one. Attackers can swallow the user's transaction and display an invalid zero-fee copy paying an attacker address, tricking users into RBF fee-bumping and signing it.

Facts

  • Vendor: spesmilo
  • Product: Electrum
  • EPSS (probability of exploitation within 30 days): 0.2 %
  • First known exploitation: 27 October 2026
  • First seen by Risk Letters: 27 October 2026

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Data: NVD (public domain), CISA KEV, FIRST EPSS, MITRE ATT&CK, AlienVault OTX. NVD