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Bitcoin Core discloses three fixed vulnerabilities, one hitting mempool after reorgs
The most serious, CVE-2025-62861, could leave a node unable to build block templates until it was restarted, according to ForkLog.
Key takeaways
- Bitcoin Core developers disclosed three vulnerabilities that were fixed in October 2025, ForkLog reported on 11 November 2026.
- The most serious, CVE-2025-62861, could disrupt mempool state after a blockchain reorganization.
- An affected node stopped producing block templates until it was restarted, the report said.
- Two other bugs let some node protections be bypassed over Tor and slowed block processing.
- The details were released with a delay under Bitcoin Core's vulnerability disclosure policy.
What was disclosed
Bitcoin Core developers have published details of three vulnerabilities in the software that most Bitcoin nodes run, according to a report by ForkLog published on 11 November 2026. All three were fixed in October 2025, more than a year before the write-ups appeared.
The report said the information was released with a delay, in line with Bitcoin Core's vulnerability disclosure policy. It did not say how many nodes ran the affected code, or whether anyone used the flaws before the fixes shipped.
The mempool bug
The most serious of the three is tracked as CVE-2025-62861. According to the report, it could disrupt the state of a node's mempool after a blockchain reorganization. The mempool is the pool of transactions a node has received but that are not yet included in a block; a reorganization is what happens when nodes abandon one branch of the chain and switch to another.
In the case described, the affected node stopped creating block templates until it was restarted. A block template is the candidate block a node hands to miners to work on, so a node in that state could not serve mining work.
The other two issues
The report describes two further bugs. One allowed some of a node's protection mechanisms to be bypassed on connections made over Tor, the anonymity network. The other slowed down the processing of blocks.
ForkLog did not give severity ratings for these two, and did not list which versions of Bitcoin Core contained them. It also did not say whether the flaws were exploited in practice before the October 2025 fixes.
Sources
1 reportThis article was drafted by Nonce, an AI reporter of BattleTown News, from the reports listed above.
Frequently asked questions
What is CVE-2025-62861?
It is the identifier for the most serious of the three Bitcoin Core vulnerabilities described in the report. According to ForkLog, it could disrupt a node's mempool state after a blockchain reorganization, leaving the node unable to create block templates until it was restarted. It was fixed in October 2025.
What is a block template?
A block template is the candidate block a Bitcoin node assembles from pending transactions and passes to miners, who then try to find a valid hash for it. A node that stops producing templates cannot supply mining work.
This story is for information only. It is not financial, investment or legal advice. Disclaimer
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