Bug 2530645

Summary: CVE-2026-56855 complyctl: golang.org/x/crypto/ssh: Denial of Service via crafted messages [fedora-all]
Product: [Fedora] Fedora Reporter: jkelly <jkelly>
Component: complyctlAssignee: Marcus Burghardt <maburgha>
Status: ASSIGNED --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: rawhideCC: go-sig, hbraswel, maburgha
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["6149aca5-d0d4-472f-b5bb-730faf189259"]}
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On:    
Bug Blocks: 2528050    

Description jkelly 2026-09-09 09:46:03 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

Previously, after a channel has been established, a malicious peer could send crafted messages that would deadlock the entire connection. Now, we handle all RFC 4254 channel messages; global requests are handled explicitly. Then, treat all other messages as a protocol error and tear the connection down instead of buffering and blocking.
Comment 1 Marcus Burghardt 2026-09-10 11:10:54 UTC 
complyctl vendors golang.org/x/crypto v0.55.0 as an indirect dependency (via go-securesystemslib in the Sigstore verification stack). However, the only usage of golang.org/x/crypto/ssh in the entire dependency graph is ssh.NewPublicKey() and ssh.FingerprintSHA256() for DSSE key fingerprinting (go-securesystemslib/dsse/verify.go). The vulnerable symbols (Dial, NewClientConn, NewControlClientConn, NewServerConn) are never called — complyctl does not establish SSH connections. The flaw is therefore not exploitable in complyctl. We will bump golang.org/x/crypto to >= v0.56.0 in a forthcoming dependency update to clear the scanner finding.
Comment 2 Marcus Burghardt 2026-09-25 10:14:45 UTC 
PR proposed in Upstream: https://github.com/complytime/complyctl/pull/884