Bitcoin Core discloses CVE-2026-117349 affecting paused pre-BIP31 peers

Bitcoin Core disclosed CVE-2026-117349 on October 28, 2026, describing an unbounded memory-growth vulnerability involving paused peers that do not support BIP31 nonced pings.

A malicious peer could remain paused while the node continued to queue announcements for that connection. Without a fixed limit on that growth, memory consumption could continue to increase over time.

The project assigned the issue a Medium severity rating and said it was easily discoverable. Bitcoin Core released fixes in versions 29.5, 30.4, 31.2 and 32.1.

The remediation disconnects peers when their send buffers stay above the relevant threshold for 20 minutes, limiting the duration of the paused state that enabled the problem.

How the vulnerability affects memory use

The issue affects a peer that lacks support for BIP31 nonced pings and remains paused. While that peer is paused, Bitcoin Core can continue queueing announcements intended for the connection.

Bitcoin Core said the resulting memory growth could reach up to 2 MB per hour for each inbound peer and up to 5 MB per hour for each outbound peer. The risk is tied to continued queueing without a fixed upper bound while the affected connection remains paused.

The disclosure concerns node software behavior and does not by itself establish that the vulnerability was exploited. Operators should review the release versions cited by Bitcoin Core when assessing whether their installations include the fix.

Fix merged before public disclosure

The mitigation was merged as Bitcoin Core pull request #36667 on October 26, 2026, before the October 28 public disclosure. It enforces a timeout interval for paused send peers.

Under the change, a peer is disconnected if its send buffer remains above the threshold for 20 minutes. This prevents an affected paused connection from continuing indefinitely under those conditions.

The release of fixed versions follows other maintenance work in the project, including the updates covered in Bitcoin Core 30.3 released with bug fixes.

• Fixed releases: Bitcoin Core 29.5
• Fixed releases: Bitcoin Core 30.4
• Fixed releases: Bitcoin Core 31.2
• Fixed releases: Bitcoin Core 32.1

Context for node operators

Bitcoin Core’s classification of the issue as Medium severity reflects the potential for memory pressure from malicious peer behavior, rather than a claim that all nodes are affected in the same way. The disclosed scenario specifically involves paused peers that do not support BIP31 nonced pings.

The report adds to the record of software security issues that can affect node operations. A separate Bitcoin Core disclosure addressed an urgent-data memory flaw affecting non-Linux nodes.

Operators can use the disclosed fixed versions and the project’s release information to determine the appropriate maintenance path for their environment.

Continue reading: Bitcoin Core 30.3 released with bug fixes on BTCNews.

Continue reading: urgent-data memory flaw affecting non-Linux nodes on BTCNews.

Sources

• Bitcoin Core: CVE-2026-117349 – Slow unbounded memory growth on paused pre-BIP31 peers
• Bitcoin Core GitHub repository: net: enforce timeout interval for paused send peers – Pull Request #36667
• Bitcoin Core GitHub repository: Bitcoin Core releases

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