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CVE-2026-102820— pageant: Out-of-bounds read / oversized allocation in `pageant` MemoryMap::read via a malicious Pageant agent (Windows)

Quick assessment

Affected
Eugeny russh
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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 pe

CVSS 6.2 · Medium
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I. Basic Information for CVE-2026-102820

Vulnerability Information

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Vulnerability Title
pageant: Out-of-bounds read / oversized allocation in `pageant` MemoryMap::read via a malicious Pageant agent (Windows)
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Eugeny russh < 0.63.2 -
rust pageant < 0.2.3 -

II. Public POCs for CVE-2026-102820

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III. Intelligence Information for CVE-2026-102820

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Other References for CVE-2026-102820 (3)

Same Patch Batch · Eugeny · 2026-09-29 · 6 CVEs total

CVE-2026-102823 7.5 HIGH russh: Client-side channel-scoped Handler callbacks fire for channel IDs the client never
CVE-2026-102821 6.5 MEDIUM Russh: Unbounded memory exhaustion via CHANNEL_OPEN flood during a client-stalled rekey
CVE-2026-102824 4.3 MEDIUM Russh: Missing X25519 zero-point validation in hybrid ML-KEM key exchange
CVE-2026-102822 3.7 LOW russh: negotiating a MAC-requiring block cipher (CTR/CBC) with mac=none causes a slice-ind
CVE-2026-102825 3.7 LOW Russh: Configured server auth-attempt cap is not enforced in the USERAUTH_REQUEST runtime

IV. Related Vulnerabilities

Same product: russh
Same vendor: Eugeny
Same weakness: CWE-125

V. Comments for CVE-2026-102820

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