spesmilo
Electrum before 4.8.3 Missing Signature Verification of Mempool Transactions
Not on CISA's list of exploited flaws, and not in the news we track.
CVE-2026-117601Critical9.3
Black Shard's team can check your exposure to CVE-2026-117601 and take the fix off your plate.
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.
Black Shard's team can check your exposure, take a fix off your plate or step in on a live incident.
Chance of exploitation in the next 30 days
0.18%
EPSS score from FIRST
Updated 13 Nov 2026, 11:37 UTC, 30 of 36 sources answering.
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