CVE-2025-14819: OpenSSL partial chain store policy bypass

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-01-08 · updated 2026-10-14
Weakness: CWE-295

Description

When doing TLS related transfers with reused easy or multi handles and altering the `CURLSSLOPT_NO_PARTIALCHAIN` option, libcurl could accidentally reuse a CA store cached in memory for which the partial chain option was reversed. Contrary to the user's wishes and expectations. This could make libcurl find and accept a trust chain that it otherwise would not.

Affected products

curl: from 7.87.0 before 8.18.0 — fixed in 8.18.0

How to fix

Upgrade to a fixed version: curl 8.18.0. Check the vendor advisory for mitigations.

References

https://curl.se/docs/CVE-2025-14819.html
https://curl.se/docs/CVE-2025-14819.json
http://www.openwall.com/lists/oss-security/2026/01/07/5

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