JLSEC-2026-410

An information disclosure vulnerability exists in curl v8.1.0 when doing HTTPS transfers, libcurl might erroneously use the read callback CURLOPTREADFUNCTION to ask for data to send, even when the CURLOPTPOSTFIELDS option has been set, if the same handle previously wasused to issue a PUT request...

JLSEC-2026-401

A use after free vulnerability exists in curl 7.87.0. Curl can be asked to tunnel virtually all protocols it supports through an HTTP proxy. HTTP proxies can and often do deny such tunnel operations. When getting denied to tunnel the specific protocols SMB or TELNET, curl would use a heap-allocat...

JLSEC-2026-438 curl would wrongly reuse an existing HTTP proxy connection doing CONNECT to a server, even if the...

curl would wrongly reuse an existing HTTP proxy connection doing CONNECT to a server, even if the new request uses different credentials for the HTTP proxy. The proper behavior is to create or use a separate connection...

JLSEC-2026-388

A insufficiently protected credentials vulnerability in fixed in curl 7.83.0 might leak authentication or cookie header data on HTTP redirects to the same host but another port number...

JLSEC-2026-428 When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer performs a...

When an OAuth2 bearer token is used for an HTTPS transfer, and that transfer performs a cross-protocol redirect to a second URL that uses an IMAP, LDAP, POP3 or SMTP scheme, curl might wrongly pass on the bearer token to the new target host...

JLSEC-2026-420 When asked to use a `.netrc` file for credentials **and** to follow HTTP redirects, curl could leak...

When asked to use a .netrc file for credentials and to follow HTTP redirects, curl could leak the password used for the first host to the followed-to host under certain circumstances. This flaw only manifests itself if the netrc file has a default entry that omits both login and password. A rare...

JLSEC-2026-407

A use after free vulnerability exists in curl v8.1.0 in the way libcurl offers a feature to verify an SSH server's public key using a SHA 256 hash. When this check fails, libcurl would free the memory for the fingerprint before it returns an error message containing the now freed hash. This flaw...

JLSEC-2026-409

An improper certificate validation vulnerability exists in curl v8.1.0 in the way it supports matching of wildcard patterns when listed as "Subject Alternative Name" in TLS server certificates. curl can be built to use its own name matching function for TLS rather than one provided by a TLS...

JLSEC-2026-386

An insufficiently protected credentials vulnerability exists in curl 4.9 to and include curl 7.82.0 are affected that could allow an attacker to extract credentials when follows HTTPS redirects is used with authentication could leak credentials to other services that exist on different protocols ...

JLSEC-2026-400

A vulnerability exists in curl 7.87.0 HSTS check that could be bypassed to trick it to keep using HTTP. Using its HSTS support, curl can be instructed to use HTTPS instead of using an insecure clear-text HTTP step even when HTTP is provided in the URL. However, the HSTS mechanism could be bypasse...

JLSEC-2026-430 When doing SSH-based transfers using either SCP or SFTP, and setting the `known_hosts` file, libcurl...

When doing SSH-based transfers using either SCP or SFTP, and setting the knownhosts file, libcurl could still mistakenly accept connecting to hosts not present in the specified file if they were added as recognized in the libssh global knownhosts file...

JLSEC-2026-423 curl's websocket code did not update the 32 bit mask pattern for each new outgoing frame as the...

curl's websocket code did not update the 32 bit mask pattern for each new outgoing frame as the specification says. Instead it used a fixed mask that persisted and was used throughout the entire connection. A predictable mask pattern allows for a malicious server to induce traffic between the two...

JLSEC-2026-395

When curl 7.84.0 does FTP transfers secured by krb5, it handles message verification failures wrongly. This flaw makes it possible for a Man-In-The-Middle attack to go unnoticed and even allows it to inject data to the client...

JLSEC-2026-398

curl before 7.86.0 has a double free. If curl is told to use an HTTP proxy for a transfer with a non-HTTPS URL, it sets up the connection to the remote server by issuing a CONNECT request to the proxy, and then tunnels the rest of the protocol through. An HTTP proxy might refuse this request HTTP...

JLSEC-2026-404

An allocation of resources without limits or throttling vulnerability exists in curl v7.88.0 based on the "chained" HTTP compression algorithms, meaning that a server response can be compressed multiple times and potentially with differentalgorithms. The number of acceptable "links" in this...

JLSEC-2026-408

A denial of service vulnerability exists in curl v8.1.0 in the way libcurl provides several different backends for resolving host names, selected at build time. If it is built to use the synchronous resolver, it allows name resolves to time-out slow operations using alarm and siglongjmp. When doi...

JLSEC-2026-397

When curl is used to retrieve and parse cookies from a HTTPS server, itaccepts cookies using control codes that when later are sent back to a HTTPserver might make the server return 400 responses. Effectively allowing a"sister site" to deny service to all siblings...

JLSEC-2026-389

The curl URL parser wrongly accepts percent-encoded URL separators like '/'when decoding the host name part of a URL, making it a different URL usingthe wrong host name when it is later retrieved.For example, a URL like http://example.com%2F127.0.0.1/, would be allowed bythe parser and get...

JLSEC-2026-394

When curl 7.84.0 saves cookies, alt-svc and hsts data to local files, it makes the operation atomic by finalizing the operation with a rename from a temporary name to the final target file name.In that rename operation, it might accidentally widen the permissions for the target file, leaving the...

JLSEC-2026-402

A cleartext transmission of sensitive information vulnerability exists in curl v7.88.0 that could cause HSTS functionality fail when multiple URLs are requested serially. Using its HSTS support, curl can be instructed to use HTTPS instead of usingan insecure clear-text HTTP step even when HTTP is...