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...

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...

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...

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...

Wrong content via Metalink not discarded

When curl is instructed to download content using the Metalink feature, the contents is verified against a hash provided in the Metalink XML file. The Metalink XML file points out to the client how to get the same content from a set of different URLs, potentially hosted by different servers and t...

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...

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...

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...

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...

wrong reuse of SMB connection

libcurl might in some circumstances reuse the wrong connection for SMBS transfers. 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 criteria must be met. Due to a logical error in the...

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...

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...

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...

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...

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...

missing SFTP host verification with wolfSSH

curl's code for managing SSH connections when SFTP was done using the wolfSSH powered backend was flawed and missed host verification mechanisms. This prevents curl from detecting MITM attackers and more...

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...

HTTP multi-header compression denial of service

curl supports "chained" HTTP compression algorithms, meaning that a server response can be compressed multiple times and potentially with different algorithms. The number of acceptable "links" in this "decompression chain" was capped, but the cap was implemented on a per-header basis allowing a...

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...

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 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-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...

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...

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...

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...

WS Auto-PONG memory exhaustion

By default, curl automatically responds to WebSocket PING frames. Because curl lacks an upper bound on memory allocation for unacknowledged frames, a malicious server can exhaust all available memory by flooding curl with rapid, sequential PING messages...

HTTP/2 stream-dependency tree UAF

A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via CURLOPTSTREAMDEPENDS or CURLOPTSTREAMDEPENDSE, subsequently invokes curleasyreset, and finally terminates the handle with curleasycleanup. During this final cleanup phase, libcurl...

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...

OpenSSL partial chain store policy bypass

When doing TLS related transfers with reused easy or multi handles and altering the CURLSSLOPTNOPARTIALCHAIN option, libcurl could accidentally reuse a CA store cached in memory for which the partial chain option was reversed. Contrary to the user's wishes and expectations. This could make libcur...

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...

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...

siglongjmp race condition

libcurl provides several different backends for resolving hostnames, 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 doing this, libcurl used a global buffer that was not mutex protected a...

SFTP path ~ resolving discrepancy

curl supports SFTP transfers. curl's SFTP implementation offers a special feature in the path component of URLs: a tilde character as the first path element in the path to denotes a path relative to the user's home directory. This is supported because of wording in the once proposed to-become RFC...

curl removes wrong file on error

curl might remove the wrong file when --no-clobber is used together with --remove-on-error. The --remove-on-error option tells curl to remove the output file when it returns an error, and not leave a partial file behind. The --no-clobber option prevents curl from overwriting a file if it already...

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 end-of-response out-of-bounds read

libcurl contains a heap out-of-bounds read in the code handling the end-of-response for SMTP. If the buffer passed to smtpendofresp is not null-terminated and contains no character ending the parsed number, and len is set to 5, then the strtol call reads beyond the allocated buffer. The read...

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...

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...

URL globbing out of bounds read

curl supports "globbing" of URLs, in which a user can pass a numerical range to have the tool iterate over those numbers to do a sequence of transfers. In the globbing function that parses the numerical range, there was an omission that made curl read a byte beyond the end of the URL if given a...

Use after free via shared cookies

libcurl explicitly allows users to share cookies between multiple easy handles that are concurrently employed by different threads. When cookies to be sent to a server are collected, the matching function collects all cookies to send and the cookie lock is released immediately afterwards. That...

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...

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...

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...

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...

SASL buffer overflow

libcurl is vulnerable to a buffer overflow vulnerability when communicating with one of the protocols POP3, SMTP or IMAP. When negotiating SASL DIGEST-MD5 authentication, the function Curlsaslcreatedigestmd5message uses the data provided from the server without doing the proper length checks and...

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...

SASL double-free

The curl logic that works with SASL authentication could end up cleaning up the GSASL context twice without clearing the pointer in between, making it free the same pointer twice...