Bug 2543500 (CVE-2026-102820)

Summary: CVE-2026-102820 pageant: pageant: Denial of Service via untrusted response length in shared memory
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in pageant. On Windows, the component fails to properly validate the response length received through shared memory when communicating with an authentication agent. A local attacker impersonating the agent can supply a manipulated length value, triggering an oversized memory allocation and an out-of-bounds memory read. This can lead to a Denial of Service (DoS) by crashing the client application and may potentially result in information disclosure.
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Description OSIDB Bzimport 2026-09-29 18:40:33 UTC 
pageant provides a [PageantStream] type that implements [AsyncRead] and [AsyncWrite] traits and can be used to talk to a running Pageant instance. Prior to pageant 0.2.3, the Windows pageant crate's pageant/src/wmmessage.rs MemoryMap::read function trusts a peer-controlled u32 response length supplied through the 8192-byte Pageant shared-memory mapping reached by AgentClient::connect_pageant. A local process that impersonates the Pageant window can make query_pageant_direct allocate up to approximately 4 GiB and copy beyond the mapped view, reliably crashing a russh client and conditionally exposing adjacent committed memory. This issue is fixed in pageant 0.2.3.