electrum

CVE-2026-117601: CVE-2026-117601: Improper Cryptographic Signature Verification in Electrum Bitcoin Wallet CVE-2026-117601: Improper Cryptographic Signature Verification in Electrum Bitcoin Wallet > Vulnerability ID: CVE-2026-117601 > CVSS Score: 9.3 > Published: 2026-10-28 A missing cryptographic signature verification vulnerability exists in Electrum Bitcoin Wallet versions prior to 4.8.3. In Electrum's Simplified Payment Verification (SPV) architecture, the client failed to validate input signatures on unconfirmed mempool transactions received from connected Electrum servers. A malicious Electrum server can exploit this flaw by intercepting a legitimate user broadcast, suppressing it, and returning a spoofed unconfirmed transaction with an invalid signature and zero fee that redirects the user's UTXOs to an attacker-controlled address. When the user initiates a Replace-By-Fee (RBF) action to accelerate the seemingly stuck transaction, Electrum signs the spoofed outputs with the user's private keys, resulting in the direct theft of funds. TL;DR Electrum Bitcoin Wallet versions prior to 4.8.3 fail to verify cryptographic signatures on wallet-owned inputs for unconfirmed transactions received from Electrum servers. A malicious server can inject a spoofed, zero-fee mempool transaction spending the user's funds to an attacker address and induce the user to sign it via a Replace-By-Fee (RBF) fee bump. --- Technical Details - Vulnerability ID: CVE-2026-117601 / GHSA-6jp4-8v48-cc5v - CWE Classification: CWE-347: Improper Verification of Cryptographic Signature - CVSS v4.0 / v3.1 Score: 9.3 (Critical) / 7.5 (High) - EPSS Score: 0.18% (7.12th Percentile) - Attack Vector: Network (Malicious Electrum Server / SPV Protocol Manipulation) - Affected Versions: Electrum < 4.8.3 - Patched Version: Electrum 4.8.3 - Primary Impact: Theft of Bitcoin funds via Replace-By-Fee (RBF) transaction poisoning Affected Systems - Electrum Bitcoin Wallet (spesmilo/electrum) - Electrum Bitcoin Wallet: < 4.8.3 (Fixed in: 4.8.3) Code Analysis Commit: 90fe308 Merge "verify_sigs": adb: check sigs of is_mine txins of unconf txs (verify signatures of wallet.is_mine inputs for mempool txs only) Mitigation Strategies - Upgrade Electrum Bitcoin Wallet to version 4.8.3 or later to enforce local cryptographic signature verification on mempool inputs. - Connect exclusively to a trusted, self-hosted Electrum server (Fulcrum, ElectrumX, or Electrs) backed by a personal full node using the --oneserver configuration flag. - Verify destination addresses and output amounts on a hardware wallet's trusted display prior to approving any Replace-By-Fee (RBF) or fee-bumping transaction. - Avoid relying on unconfirmed (0-conf) transaction states for automated financial workflows or point-of-sale systems. Remediation Steps: 1. Download the official Electrum 4.8.3 (or newer) release package from the official project repository or website. 2. Verify the GPG signature of the downloaded Electrum binary or source tarball against the maintainers' public keys. 3. Install the updated version and restart any running Electrum GUI or headless daemon instances. 4. In Electrum Network Settings (Tools -> Network), optionally disable 'Select server automatically' and configure a known trusted server endpoint. References - GitHub Security Advisory GHSA-6jp4-8v48-cc5v - Electrum Patch Commit 90fe30822561e515a9d2d6e5a352cc07780999eb - VulnCheck Advisory: Electrum before 4.8.3 Missing Signature Verification of Mempool Transactions - NVD - CVE-2026-117601 - CVE.org Record: CVE-2026-117601 - CVE List V5 JSON Record for CVE-2026-117601 --- Read the full report for CVE-2026-117601 on our website for more details including interactive diagrams and full exploit analysis.

Our eWallet was also prone to an exploit described at github.com/spesmilo/electrum/security/advisories/… since it also relies on Electrum servers. An exploit is properly fixed in v4.1-22 (github.com/Tactical-Advantage-Trading/wallet/rele…).

Electrum patched a bug that let a malicious server swap your pending payment for a fake one Hit "speed up" and you could sign coins over to the attacker Anyone on their own server wasn't exposed Update to 4.8.3. Better yet, run your own node github.com/spesmilo/electrum/security/advisories/…

Electrum's "bump fee" button could pay a thief. A shady server hid your real tx and showed a fake one to the attacker, so bumping it signed the theft. Seen in the wild. What to do: Update to 4.8.3 and check the full address before any fee bump. #Bitcoin github.com/spesmilo/electrum/security/advisories/…

@coinbureau hardware didnt save anyone from the other attack this week either. electrum user1 verified on 2 trezors. a fee bump would have put a lookalike on the trezor screen that matched the last 4 chars. 58^4 = 11.3m tries, i ground one in 38s. advisory: github.com/spesmilo/electrum/security/advisories/…

Security exploit in electrum. Update to new version 4.8.3 from official website only. Source: x.com Source: github.com/spesmilo/electrum/security/advisories/… > Malicious server can replace a just-broadcast tx and try to trick user into RBF-ing it > Summary > The main Electrum server the client connects to is trusted with mempool ("unconfirmed") transactions. This is documented design. [0] > However now someone figured out a way to practically exploit it: > * when the client broadcasts a new tx1, a malicious server can swallow it, > * and update the client's history with a conflicting (invalid) tx2 that replaces the outputs with the attacker's output address. > * Tx2 has invalid signatures, but this is not checked (due to light client design). > * The wallet will display tx2 as an unconfirmed transaction - tx1 will not be displayed. > * If the client then manually RBF fee-bumps tx2, the client will sign it with a higher fee, and hence pay the attacker. > Fixes > Commit 90fe308 contains the fix [1], included in version 4.8.3. > The client now verifies the signatures of wallet.is_mine inputs for mempool txs (before adding them to its local history). > Users should upgrade (and regularly do so in any case). > As a workaround, without upgrading, when signing any transaction, for bumping the fee or not, they should verify the output addresses and amounts are as expected. >Clients that connect to servers they trust (e.g. run their own) are not affected. >Remarks > * some servers are performing this attack in the wild > * we received two user-reports of this. user1 noticed after broadcasting tx1 the wallet history contained a different tx. user2 bumped the fee of tx2 and lost money. > * user1 reported tx1 was not propagated over the bitcoin p2p, so the server held it > * both reported the attacker's output address in tx2 was grinded to match the last four chars of the legit address from tx1 > * based on user2's report, the server constructed a tx2 with zero fee (presumably in hope of the user bumping its fee) > * even with the fix, we still only validate "is_mine" inputs (i.e. paying from addresses that the wallet owns). So e.g. "incoming" txs are not validated. The client lacks a full consensus engine / script interpreter, though even with that, to cover non-is_mine inputs, it would have to validate the unconfirmed parents recursively until reaching mined txs. > Mined txs we already SPV. > Timeline > * 2026-10-11: user1 (dannydeezy) sends private disclosure, but the bump_fee vector is not realised > * 2026-10-18: user2 (Raju-K12) reports privately that they lost money after bump_fee > * 2026-10-23: version 4.8.3 git tagged, with the fix > * 2026-10-24: version 4.8.3 binaries released > * 2026-10-24: public disclosure > Credits > We thank dannydeezy and Raju-K12 for finding and responsibly disclosing this issue to us.

Bitcoinウォレット「Electrum」4.8.3未満に、深刻度Highの脆弱性。接続先の悪意あるサーバーが、送ったばかりの取引を宛先だけ攻撃者のアドレス（末尾4文字を本物に似せたもの）に変えた偽物にすり替えて表示。それに手数料の上乗せ（RBF）をすると攻撃者に支払ってしまう。実際に悪用され、資金を失った報告あり。4.8.3に更新を。更新前は署名時に送金先と金額を必ず確認。自前サーバー接続なら影響なし。 github.com/spesmilo/electrum/security/advisories/…

Critical Security Exploit in Electrum. Upgrade to version 4.8.3 before signing any transactions Critical Security Exploit in Electrum. Upgrade to version 4.8.3 before signing any transactions. No rush needed for dormant/cold wallets although you should remember upgrading before using electrum. x.com Explanation of Exploit github.com/spesmilo/electrum/security/advisories/… Download update directly from source electrum.org In general LLM models have been discovering critical security vulnerabilities in general much faster than in the past which is both a headache and blessing at the same time as much more peer review is occurring and the software is becoming more secure. This does mean that you need to update all your software more often and pay attention to security updates to a much higher degree at least for the next year.

Critical Security Exploit in Electrum. Upgrade to version 4.8.3 before signing any transactions Critical Security Exploit in Electrum. Upgrade to version 4.8.3 before signing any transactions. No rush needed for dormant/cold wallets although you should remember upgrading before using electrum. x.com Explanation of Exploit github.com/spesmilo/electrum/security/advisories/… Download update directly from source electrum.org In general LLM models have been discovering critical security vulnerabilities in general much faster than in the past which is both a headache and blessing at the same time as much more peer review is occurring and the software is becoming more secure. This does mean that you need to update all your software more often and pay attention to security updates to a much higher degree at least for the next year.

Critical Security Exploit in Electrum. Upgrade to version 4.8.3 before signing any transactions Critical Security Exploit in Electrum. Upgrade to version 4.8.3 before signing any transactions. No rush needed for dormant/cold wallets although you should remember upgrading before using electrum. x.com Explanation of Exploit github.com/spesmilo/electrum/security/advisories/… Download update directly from source electrum.org In general LLM models have been discovering critical security vulnerabilities in general much faster than in the past which is both a headache and blessing at the same time as much more peer review is occurring and the software is becoming more secure. This does mean that you need to update all your software more often and pay attention to security updates to a much higher degree at least for the next year.