# MongoDB Python Driver: Out-of-bounds read in BSON decoding via a malformed Regex element

Advisory record · `GHSA-98qm-wvgf-w4cf`

- **Identifiers:** `GHSA-98qm-wvgf-w4cf` · `CVE-2026-106435`
- **State:** Confirmed
- **Severity:** CVSS 5.9 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-125](https://cwe.mitre.org/data/definitions/125.html)
- **Tags:** [Memory corruption](https://agentprime.io/advisories/tag/memory-corruption.md)
- **Published:** 27 Oct 2026
- **Updated:** 27 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 27 Oct 2026, 15:36 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `pymongo` (PyPI): affected `>=3.9.0, <4.18.3`; fixed in `4.18.3`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 5.9 Medium, CVSS 4.0: `CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`, from CNA (mongodb)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0009, the 1st percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:07 UTC: First seen by agentprime
- 31 Oct 2026, 14:07 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-98qm-wvgf-w4cf)

## Sources

- [GitHub Advisory Database: GHSA-98qm-wvgf-w4cf](https://github.com/advisories/GHSA-98qm-wvgf-w4cf)
- [OSV: GHSA-98qm-wvgf-w4cf](https://osv.dev/vulnerability/GHSA-98qm-wvgf-w4cf)
- <https://github.com/mongodb/mongo-python-driver/security/advisories/GHSA-98qm-wvgf-w4cf>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-106435>
- <https://github.com/mongodb/mongo-python-driver/pull/3109>
- <https://github.com/mongodb/mongo-python-driver/commit/bb8d4e195275e75bd94ebeffb53cc747d357fcf4>
- <https://github.com/mongodb/mongo-python-driver>
- <https://github.com/mongodb/mongo-python-driver/releases/tag/4.18.3>
- <https://jira.mongodb.org/browse/PYTHON-6110>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-98qm-wvgf-w4cf>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-98qm-wvgf-w4cf/>. Everything for agents: <https://agentprime.io/llms.txt>.