Vulnerability · Published Oct 20, 2026 · Assigned by curl
CVE-2026-87866wolfSSL public-key pinning bypass
Critical 9.1
In plain English
A critical-severity improper certificate validation in curl from curl. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
When built with wolfSSL, curl can successfully validate a pinned public key hash against a key the TLS peer does not possess. During the TLS handshake, wolfSSL validates the connection, but curl's subsequent re-parsing of the same certificate - tricked by a manipulated validity length field - extracts and matches a different embedded key, incorrectly authorizing the pinned public key.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | curl | 8.23.0-r0 | ALPINE-CVE-2026-87866 |
| Alpine:v3.24 | curl | 8.23.0-r0 | ALPINE-CVE-2026-87866 |
| Debian:12 | curl | no fix listed | DEBIAN-CVE-2026-87866 |
| Debian:13 | curl | no fix listed | DEBIAN-CVE-2026-87866 |
| Debian:14 | curl | no fix listed | DEBIAN-CVE-2026-87866 |
Affected products (as reported)
Weakness: CWE-295 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N