Bug 2562942 (CVE-2026-116774)

Summary: CVE-2026-116774 russh: russh: Denial of service via zero maximum packet size
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in russh. An authenticated remote client or a malicious server can cause a denial of service (DoS) by declaring a maximum packet size of zero during SSH channel negotiation. The affected system accepts this value, causing asynchronous write operations to hang indefinitely and allowing stranded tasks, channels, and connections to accumulate without raising an error.
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Description OSIDB Bzimport 2026-10-28 16:32:33 UTC 
russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. From 0.60.0 until 0.65.0, channel-open parsing accepts a peer-declared maximum_packet_size of zero and passes it into ChannelTx::poll_writable in russh/src/channels/io/tx.rs. The Channel::data, Channel::make_writer, and Channel::into_stream asynchronous write paths then calculate a writable size of zero and remain pending forever because window adjustments cannot satisfy a static zero packet maximum. An authenticated client can strand server writes, and a malicious server can strand client writes, allowing affected tasks, channels, and connections to accumulate without surfacing an error. This issue is fixed in version 0.65.0.