Windows OpenSSL engine code injection

A non-privileged user or program can put code and a config file in a known non-privileged path under C:/usr/local/ that makes curl automatically run the code as an OpenSSL "engine" on invocation. If that curl is invoked by a privileged user it can do anything it wants. This flaw exists in the...

RTSP bad headers buffer over-read

curl can be tricked into reading data beyond the end of a heap based buffer used to store downloaded content. When servers send RTSP responses back to curl, the data starts out with a set of headers. curl parses that data to separate it into a number of headers to deal with those appropriately an...

sensitive HTTP server headers also sent to proxies

libcurl provides applications a way to set custom HTTP headers to be sent to the server by using CURLOPTHTTPHEADER. A similar option is available for the curl command-line tool with the '--header' option. When the connection passes through an HTTP proxy the same set of headers is sent to the prox...

broken TLS options for threaded LDAPS

When doing multi-threaded LDAPS transfers LDAP over TLS with libcurl, changing TLS options in one thread would inadvertently change them globally and therefore possibly also affect other concurrently setup transfers. Disabling certificate verification for a specific transfer could unintentionally...

FTP-KRB double free

libcurl can be told to use kerberos over FTP to a server, as set with the CURLOPTKRBLEVEL option. During such kerberos FTP data transfer, the server sends data to curl in blocks with the 32-bit size of each block first and then that amount of data immediately following. A malicious or broken serv...

TFTP receive buffer overflow

libcurl contains a heap buffer overflow in the function tftpreceivepacket that receives data from a TFTP server. It calls recvfrom with the default size for the buffer rather than with the size that was used to allocate it. Thus, the content that might overwrite the heap memory is entirely...

RTSP RTP buffer over-read

curl can be tricked into copying data beyond end of its heap based buffer. When asked to transfer an RTSP URL, curl could calculate a wrong data length to copy from the read buffer. The memcpy call would copy data from the heap following the buffer to a storage area that would subsequently be...

IMAP FETCH response out of bounds read

libcurl contains a buffer overrun flaw in the IMAP handler. An IMAP FETCH response line indicates the size of the returned data, in number of bytes. When that response says the data is zero bytes, libcurl would pass on that non-existing data with a pointer and the size zero to the deliver-data...

TFTP sends more than buffer size

When doing a TFTP transfer and curl/libcurl is given a URL that contains a long filename longer than about 515 bytes, the filename is truncated to fit within the buffer boundaries, but the buffer size is still wrongly updated to use the original length. This too large value is then used in the...

reuse of wrong HTTP NTLM connection

libcurl can in some circumstances reuse the wrong connection when asked to do an NTLM-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criterion...

trailing dot domain super cookie

A flaw in curl’s cookie parsing logic allows a malicious HTTP server to set "super cookies" that bypass the Public Suffix List check. This enables an attacker-controlled origin to inject cookies that curl subsequently scopes and transmits to unrelated third-party domains...

Native CA trust persist

libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if one of them matches the setup. An easy handle that first uses default native CA trust can continue trusting the native platform store after the application switches that same handle to custom CA...

netrc and redirect credential leak

When asked to both 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 an entry that matches the redirect target hostname but...

ASN.1 date parser overread

libcurl's ASN1 parser code has the GTime2str function, used for parsing an ASN.1 Generalized Time field. If given an syntactically incorrect field, the parser might end up using -1 for the length of the time fraction, leading to a strlen getting performed on a pointer to a heap buffer area that i...

freeing stack buffer in utf8asn1str

libcurl's ASN1 parser has this utf8asn1str function used for parsing an ASN.1 UTF-8 string. It can detect an invalid field and return error. Unfortunately, when doing so it also invokes free on a 4 byte local stack buffer. Most modern malloc implementations detect this error and immediately abort...

macidn punycode buffer overread

libcurl's URL API function curlurlget offers punycode conversions, to and from IDN. Asking to convert a name that is exactly 256 bytes, libcurl ends up reading outside of a stack based buffer when built to use the macidn IDN backend. The conversion function then fills up the provided buffer exact...

STARTTLS protocol injection via MITM

When curl connects to an IMAP, POP3, SMTP or FTP server to exchange data securely using STARTTLS to upgrade the connection to TLS level, the server can still respond and send back multiple responses before the TLS upgrade. Such multiple pipelined responses are cached by curl. curl would then...

TLS 1.3 session ticket proxy host mix-up

Enabled by default, libcurl supports the use of TLS 1.3 session tickets to resume previous TLS sessions to speed up subsequent TLS handshakes. When using an HTTPS proxy and TLS 1.3, libcurl can confuse session tickets arriving from the HTTPS proxy but work as if they arrived from the remote serve...

FTP shutdown response buffer overflow

curl might overflow a heap based memory buffer when closing down an FTP connection with long server command replies. When doing FTP transfers, curl keeps a spare "closure handle" around internally that is used when an FTP connection gets shut down since the original curl easy handle is then alrea...

LDAP NULL pointer dereference

curl might dereference a near-NULL address when getting an LDAP URL. The function ldapgetattributeber is called to get attributes, but it turns out that it can return LDAPSUCCESS and still return a NULL pointer in the result pointer when getting a particularly crafted response. This was a surpris...

curl escape and unescape integer overflows

The four libcurl functions curlescape, curleasyescape, curlunescape and curleasyunescape perform string URL percent escaping and unescaping. They accept custom string length inputs in signed integer arguments. The functions having names without "easy" being the deprecated versions of the others...

Negotiate not treated as connection-oriented

libcurl keeps a pool of its last few connections around after use to facilitate easy, convenient and completely transparent connection reuse for applications. When doing HTTP requests Negotiate authenticated, the entire connection may become authenticated and not only the specific HTTP request...

hostname out of boundary memory access

There is a private function in libcurl called fixhostname that removes a trailing dot from the hostname if there is one. The function is called after the hostname has been extracted from the URL libcurl has been told to act on. If a URL is given with a zero-length hostname, like in "http://:80" o...

env-set cross-proxy Digest auth state leak

When reusing a libcurl handle for sequential transfers driven by environment-variable proxy configuration, libcurl fails to clear the proxy authentication state between requests. Specifically, if the initial transfer authenticates against proxyA using Digest auth, a subsequent transfer routed...

libssh global known_hosts override

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...

QUIC certificate check skip with wolfSSL

libcurl accidentally skips the certificate verification for QUIC connections when connecting to a host specified as an IP address in the URL. Therefore, it does not detect impostors or man-in-the-middle attacks...

FILE buffer read out of bounds

When asking to get a file from a file:// URL, libcurl provides a feature that outputs meta-data about the file using HTTP-like headers. The code doing this would send the wrong buffer to the user stdout or the application's provide callback, which could lead to other private data from the heap to...

uninitialized random

libcurl's new internal function that returns a good 32-bit random value was implemented poorly and overwrote the pointer instead of writing the value into the buffer the pointer pointed to. This random value is used to generate nonces for Digest and NTLM authentication, for generating boundary...

Windows DLL hijacking

libcurl would load Windows system DLLs in a manner that may make it vulnerable to a DLL hijacking aka binary planting attack in certain configurations. libcurl has a unified code base that builds and runs on a multitude of different versions of Windows. To make that possible, when libcurl is buil...

remote filename path traversal in curl tool for Windows

curl does not sanitize colons in a remote filename that is used as the local filename. This may lead to a vulnerability on systems where the colon is a special path character. Currently Windows is the only OS where this vulnerability applies. curl offers command line options --remote-name also...

SMB send off unrelated memory contents

libcurl can get tricked by a malicious SMB server to send off data it did not intend to. In libcurl's state machine function handling the SMB protocol smbrequeststate, two length and offset values are extracted from data that has arrived over the network, and those values are subsequently used to...

not verifying certs for TLS to IP address / Secure Transport

When asked to do a TLS connection HTTPS, FTPS, IMAPS, etc to a URL specified with an IP address instead of a name, libcurl would wrongly not verify the server's name in the certificate. The signature whether it was signed by a trusted CA and validity whether the date was within the certificate's...

URL decode buffer boundary flaw

libcurl is vulnerable to a case of bad checking of the input data which may lead to heap corruption. The function curleasyunescape decodes URL encoded strings to raw binary data. URL encoded octets are represented with %HH combinations where HH is a two-digit hexadecimal number. The decoded strin...

domain-scoped PSL domain cookie

When libpsl support is enabled, libcurl fails to enforce the Public Suffix List boundary check when processing a Set-Cookie header where the Domain attribute explicitly matches an origin host that is itself a public suffix e.g., Domain=co.uk set by co.uk. Instead of coercing it into a strict...

exposing HTTP/3 early data

In this scenario, libcurl first uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate. When libcurl returns to the hostname the second time with a cached SSL...

wrong STARTTLS connection reuse

A vulnerability exists where a new transfer that uses STARTTLS to upgrade the connection might reuse an existing live connection even though the TLS configuration mismatches so it should not...

proxy credentials leak over redirect-to proxy

curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following conditions are true: 1. curl is setup to use specific different proxies for different URL schemes 2. the first proxy needs credentials 3. the second proxy uses no credentials 4. whil...

No QUIC certificate pinning with GnuTLS

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...

WebSocket endless loop

Due to a mistake in libcurl's WebSocket code, a malicious server can send a particularly crafted packet which makes libcurl get trapped in an endless busy-loop. There is no other way for the application to escape or exit this loop other than killing the thread/process. This might be used to DoS...

eventfd double close

libcurl would wrongly close the same eventfd file descriptor twice when taking down a connection channel after having completed a threaded name resolve...

TLS certificate check bypass with mbedTLS

libcurl did not check the server certificate of TLS connections done to a host specified as an IP address, when built to use mbedTLS. libcurl would wrongly avoid using the set hostname function when the specified hostname was given as an IP address, therefore completely skipping the certificate...

Another HSTS bypass via IDN

curl's HSTS check 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. The HSTS mechanism could be bypassed if the hostname in the given URL first uses...

Bad connection reuse due to flawed path name checks

libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse, if one of them matches the setup. Due to errors in the logic, the config matching function did not take 'issuer cert' into account and it compared the involved paths case insensitively, which could...

TLS session caching disaster

libcurl can be tricked into using already freed memory when a new TLS session is negotiated or a client certificate is requested on an existing connection. For example, this can happen when a TLS server requests a client certificate on a connection that was established without one. A malicious...

TELNET stack contents disclosure

curl supports the -t command line option, known as CURLOPTTELNETOPTIONS in libcurl. This rarely used option is used to send variable=content pairs to TELNET servers. Due to flaw in the option parser for sending NEWENV variables, libcurl could be made to pass on uninitialized data from a stack bas...

Partial password leak over DNS on HTTP redirect

libcurl can be tricked to prepend a part of the password to the hostname before it resolves it, potentially leaking the partial password over the network and to the DNS servers. libcurl can be given a username and password for HTTP authentication when requesting an HTTP resource - used for HTTP...

SMTP send heap buffer overflow

curl might overflow a heap based memory buffer when sending data over SMTP and using a reduced read buffer. When sending data over SMTP, curl allocates a separate "scratch area" on the heap to be able to escape the uploaded data properly if the uploaded data contains data that requires it. The si...

Reusing authenticated connection when unauthenticated

libcurl keeps a pool of its last few connections around after use to facilitate easy, convenient and completely transparent connection reuse for applications. When doing HTTP requests NTLM authenticated, the entire connection becomes authenticated and not only the specific HTTP request which is...

cert name check ignore with GnuTLS

This issue is almost identical to the one named CVE-2013-4545, but this problem affects a different SSL backend. libcurl is vulnerable to a case of missing out the checking of the certificate CN or SAN name field when the digital signature verification is turned off. libcurl offers two separate a...

embedded zero in cert name

SSL and TLS Server certificates contain one or more fields with server name or otherwise matching patterns. These strings are stored as content and length within the certificate, and thus there is no particular terminating character. curl's OpenSSL interfacing code did faulty assumptions about...