JLSEC-2026-399

In curl before 7.86.0, the HSTS check could be bypassed to trick it into staying with HTTP. Using its HSTS support, curl can be instructed to use HTTPS directly instead of using an insecure cleartext HTTP step even when HTTP is provided in the URL. This mechanism could be bypassed if the host nam...

JLSEC-2026-385

An improper authentication vulnerability exists in curl 7.33.0 to and including 7.82.0 which might allow reuse OAUTH2-authenticated connections without properly making sure that the connection was authenticated with the same credentials as set for this transfer. This affects SASL-enabled protocol...

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-2026-389

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-2026-408

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-2026-402

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...

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-2026-437 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 redirect to a second URL, curl could leak that token to the second hostname under some circumstances. If the hostname that the first request is redirected to has information in the used .netrc file, with eithe...

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

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-2026-404

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-2026-405

A vulnerability in input validation exists in curl 8.0 during communication using the TELNET protocol may allow an attacker to pass on maliciously crafted user name and "telnet options" during server negotiation. The lack of proper input scrubbing allows an attacker to send content or perform...

JLSEC-2026-419 When curl is asked to use HSTS, the expiry time for a subdomain might overwrite a parent domain's...

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 curl using applications that enable HSTS and use URLs with the insecure HTTP:// scheme and perform transfers with host...

JLSEC-2026-439 When doing a second SMB request to the same host again, curl would wrongly use a data pointer...

When doing a second SMB request to the same host again, curl would wrongly use a data pointer pointing into already freed memory...

JLSEC-2026-426 When using `CURLOPT_PINNEDPUBLICKEY` option with libcurl or `--pinnedpubkey` with the curl tool...

When using CURLOPTPINNEDPUBLICKEY option with libcurl or --pinnedpubkey with the curl tool,curl should check the public key of the server certificate to verify the peer. This check was skipped in a certain condition that would then make curl allow the connection without performing the proper chec...

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-2026-386

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

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-2026-438 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-2026-400

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...