CVE-2026-87863

When invoked with --remote-header-name (-J), curl fails to preserve its documented anti-clobbering protection if an intermediate 103 Early Hints response precedes the final HTTP response, or if an ETag header is processed before Content-Disposition under --etag-save. This flaw allows a remote HTTP server to overwrite files.

A flaw in the curl command line tool's logic makes it only set SSH host verification options when interacting directly using SFTP or SCP, and not as a result of following a redirect. This means --knownhosts, --hostpubsha256, and --hostpubmd5 are never installed when the initial URL is HTTPS.

When curl is built with GnuTLS, a malicious WebSocket server can make curl send memory past its send buffer. This is due to an out of bounds read following when gnutls_record_send() returns a number of bytes sent greater than the number of bytes it was given to send.

When writing a long cookie name and value to a Netscape cookie jar, a remote HTTP server can make curl write a record that exceeds its line-length parsing limit. Consequently, any subsequent curl invocation reading from that same cookie jar using --cookie will silently abort parsing prematurely.

When CURLOPT_INTERFACE (or the command line tool's --interface option) is set with one of the documented prefixes (if!, host!, ifhost!), that binding is not part of the connection reuse key, so a later transfer asking for a different source can silently reuse an existing connection.

A remote HTTP server can set a cookie that curl accepts and writes to a Netscape cookie jar but cannot reload. On the next invocation using the same path for --cookie and --cookie-jar, curl fails before connecting, then the cleanup procedure replaces the jar with an empty file, deleting cookies.

When curl is asked to use HSTS, the expiry time for a subdomain might overwrite a parent domain's cache entry, making it end sooner or later than otherwise intended. This affects applications using HSTS and URLs with the insecure HTTP:// scheme.

Importing a includeSubDomains parent HSTS entry before a longer-lived child entry silently drops the child. Consequently, when the parent expires, the child's valid HSTS policy is lost, causing curl to issue unencrypted HTTP requests rather than upgrading to HTTPS.

When curl uses a .netrc file for credentials and a URL with a username (without password) is specified, curl may wrongly retrieve and use the password of another user from .netrc for that host if no match exists for the specified user.

A double-free vulnerability has been found in the curl library's SASL authentication handling. The GSASL context is cleaned up twice without clearing the pointer, causing free() to be called on the same memory region twice.