CVE-2026-87866
Description
A flaw was found in curl. This vulnerability allows a malicious server to bypass public key pinning when curl is built with the wolfSSL backend. By presenting a specially crafted certificate with a manipulated validity length field, the attacker can trick curl into improperly re-parsing the certificate and authorizing an invalid key during the Transport Layer Security (TLS) handshake.
Statement
This vulnerability is rated as having a Low severity because standard Red Hat distributions compile curl against OpenSSL rather than wolfSSL, significantly limiting exposure. Exploitation strictly requires applications to link against a wolfSSL-backed build of libcurl and enable pinned public key verification. Furthermore, a successful bypass relies on an attacker providing an intricately crafted certificate accepted by the underlying TLS library, leaving typical client deployments unimpacted.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.7 | N/A | 9.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| Integrity Impact | Low | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Integrity,Authentication
Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity
When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The product might connect to a malicious host while believing it is a trusted host, or the product might be deceived into accepting spoofed data that appears to originate from a trusted host.
Acknowledgements
Red Hat would like to thank Muhamad Arga Reksapati for reporting this issue.
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