Use After Free Affecting openssl package, versions [4.0.1,4.0.3)
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-CONAN-OPENSSL-20537022
- published6 Oct 2026
- disclosed29 Sept 2026
- creditTim Becker
Introduced: 29 Sep 2026
NewCVE-2026-84783 (opens in a new tab)How to fix?
Upgrade openssl to version 4.0.3 or higher.
Overview
Affected versions of this package are vulnerable to Use After Free in the X.509 extension cache, which computes the cache under a read lock and then installs the result under a write lock, so concurrent threads each install their own result and free the previous one while another thread still holds a pointer into it. An attacker can crash a multithreaded process by driving concurrent connections whose chains build to the same trusted CA. This affects only 4.0, requires more than one thread performing certificate verification at once, and the dereference is a read rather than a write.