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CVE-2026-56855 is a denial-of-service vulnerability in the connection multiplexer of golang.org/x/crypto/ssh. After an SSH channel has been established, a malicious peer can transmit crafted or unhandled RFC 4254 channel messages that are buffered without appropriate handling, causing processing to block and deadlock the entire SSH connection. Fixed versions explicitly handle RFC 4254 channel messages and global requests, and reject other unexpected messages as protocol errors by closing the connection rather than buffering and blocking.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
26 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A denial-of-service vulnerability in golang.org/x/crypto/ssh, addressed by the rootlesskit-3.2.0-1.fc43 Fedora 43 security update, which can be triggered through crafted messages.
A vulnerability in RootlessKit resolved by the rootlesskit 3.2.0-1.fc46 update. The content provides no technical details about impact or vulnerability type.
A vulnerability referenced by the Fedora doctl security advisory; no technical vulnerability details are provided.
A vulnerability addressed by Fedora advisory FEDORA-2026-ec725c24c1 for Fedora 46/rootlesskit. The content provides no technical vulnerability details.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.