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

> A malicious local Pageant agent can trigger an out-of-bounds read and oversized allocation in the Rust pageant library, causing crashes or memory exposure.

- **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Sep 2026
- **Updated:** 30 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-102820, GHSA-g4mp-vgx3-xrvm, UBUNTU-CVE-2026-102820

## What is CVE-2026-102820?

CVE-2026-102820 is a medium-severity memory corruption vulnerability in Eugeny pageant, published on 29 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-789 (Memory Allocation with Excessive Size Value), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-102820?

2 open source packages ship an affected version, including pageant.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `pageant` | crates.io | All versions | 0.2.3 |
| `pageant` | crates.io | All versions | 0.2.3 |

## How do I fix CVE-2026-102820?

Upgrade pageant to 0.2.3 or later.

## Is CVE-2026-102820 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-102820 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-102820 and fix it if it is affected.

What it is: CVE-2026-102820 is a medium-severity memory corruption vulnerability in Eugeny pageant, published on 29 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-102820 exists.

Affected packages and fixed versions:
- pageant (crates.io): affected all versions; fixed in 0.2.3
- pageant (crates.io): affected all versions; fixed in 0.2.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-102820/ (Markdown: https://insights.sbomify.com/CVE-2026-102820/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-102820
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-102820
- OSV: https://osv.dev/vulnerability/CVE-2026-102820

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-102820/
Summaries are generated and may contain mistakes; the official description above is the record.