# CVE-2026-9545

## Summary

- **CVE ID:** CVE-2026-9545
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)
- **CWE:** CWE-200
- **Published:** Jul 3, 2026
- **Last Modified:** Sep 17, 2026

## Description

In this scenario, libcurl first uses a proper HTTP/3 server for the initial
transfers, and when it makes a second transfer to the same site it has been
replaced by the attacker's impostor machine - without a valid certificate.

When libcurl returns to the hostname the second time with a cached SSL session
(`CURLOPT_SSL_SESSIONID_CACHE` is not disabled) and early data enabled (the
`CURLSSLOPT_EARLYDATA` bit is set in `CURLOPT_SSL_OPTIONS`), libcurl might
send off the second request's bytes on that new connection *before* enforcing
the certificate verification failure. Potentially leaking sensitive
information.

## Affected Products

- curl — curl (8.20.0)
- curl — curl (8.19.0)
- curl — curl (8.18.0)
- curl — curl (8.17.0)
- curl — curl (8.16.0)
- curl — curl (8.15.0)
- curl — curl (8.14.1)
- curl — curl (8.14.0)
- curl — curl (8.13.0)
- curl — curl (8.12.1)
- curl — curl (8.12.0)
- curl — curl (8.11.1)
- curl — curl (8.11.0)
- curl — curl (962097b8dd44ed5b9e7984bc1cdffdbdd566857f)

## References

- [CNA](https://curl.se/docs/CVE-2026-9545.json)
- [CNA](https://curl.se/docs/CVE-2026-9545.html)
- [CNA](https://hackerone.com/reports/3752888)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.27%
- **EPSS Percentile:** 19.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._