CVE-2026-9545 Affecting curl package, versions <8.21.0-r0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-ALPINE324-CURL-17717489
- published30 Jun 2026
- disclosed3 Jul 2026
Introduced: 30 Jun 2026
NewCVE-2026-9545 (opens in a new tab)How to fix?
Upgrade Alpine:3.24 curl to version 8.21.0-r0 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream curl package and not the curl package as distributed by Alpine.
See How to fix? for Alpine:3.24 relevant fixed versions and status.
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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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.