Schannel cipher selection surprise

libcurl lets applications specify which specific TLS ciphers to use in transfers, using the option called CURLOPTSSLCIPHERLIST. The cipher selection is used for the TLS negotiation when a transfer is done involving any of the TLS based transfer protocols libcurl supports, such as HTTPS, FTPS,...

trusting FTP PASV responses

When curl performs a passive FTP transfer, it first tries the EPSV command and if that is not supported, it falls back to using PASV. Passive mode is what curl uses by default. A server response to a PASV command includes the IPv4 address and port number for the client to connect back to in order...

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...

use after free in handle close

libcurl contains a heap use after free flaw in code related to closing an easy handle. When closing and cleaning up an "easy" handle in the Curlclose function, the library code first frees a struct without clearing the pointer and might then subsequently erroneously write to a struct field within...

SSL out of buffer access

libcurl contains an out boundary access flaw in SSL related code. When allocating memory for a connection the internal struct called connectdata, a certain amount of memory is allocated at the end of the struct to be used for SSL related structs. Those structs are used by the particular SSL libra...

NTLM buffer overflow via integer overflow

libcurl contains a buffer overrun flaw in the NTLM authentication code. The internal function Curlntlmcoremkntlmv2hash sums up the lengths of the username + password = SUM and multiplies the sum by two = SIZE to figure out how large storage to allocate from the heap. The SUM value is subsequently...

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...

Win CE Schannel cert name out of buffer read

curl's TLS server certificate checks are flawed on Windows CE. This vulnerability occurs in the verify certificate function when comparing a wildcard certificate name as returned by the Windows API function CertGetNameString to the hostname used to make the connection to the server. The pattern...

double free in curl_maprintf

The libcurl API function called curlmaprintf can be tricked into doing a double free due to an unsafe sizet multiplication, on systems using 32-bit sizet variables. The function is also used internally in numerous situations. The function doubles an allocated memory area with realloc and allows t...

curl_getdate read out of bounds

The curlgetdate converts a given date string into a numerical timestamp and it supports a range of different formats and possibilities to express a date and time. The underlying date parsing function is also used internally when parsing for example HTTP cookies possibly received from remote serve...

NTLM credentials not-checked for proxy connection reuse

libcurl reuses NTLM-authenticated proxy connections without properly making sure that the connection was authenticated with the same credentials as set for this transfer. libcurl maintains a pool of connections after a transfer has completed. The pool of connections is then gone through when a ne...

inappropriate GSSAPI delegation

When doing GSSAPI authentication, libcurl unconditionally performs credential delegation. This hands the server a copy of the client's security credentials, allowing the server to impersonate the client to any other using the same GSSAPI mechanism. This is obviously a sensitive operation, which...

Out of bounds read for cookie path

A cookie is set using the secure keyword for https://target 2. curl is redirected to or otherwise made to speak with http://target same hostname, but using clear text HTTP using the same cookie set 3. The same cookie name is set - but with only a slash as path path="/". Since this site is not...

HSTS subdomain overwrites parent cache entry

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...

Usage of disabled protocol

When a protocol selection parameter option disables all protocols without adding any then the default set of protocols would remain in the allowed set due to an error in the logic for removing protocols. The below command would perform a request to curl.se with a plaintext protocol which has been...

HTTP headers eat all memory

When curl retrieves an HTTP response, it stores the incoming headers so that they can be accessed later via the libcurl headers API. However, curl did not have a limit on the size or quantity of headers it would accept in a response, allowing a malicious server to stream an endless series of...

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...

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...

control code in cookie denial of service

When curl retrieves and parses cookies from an HTTPS server, it accepts cookies using control codes byte values below 32. When cookies that contain such control codes are later sent back to an HTTPS server, it might make the server return a 400 response. Effectively allowing a "sister site" to de...

HTTP 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 unbounded, allowing a malicious server to insert a virtually unlimited...

CERTINFO never-ending busy-loop

libcurl provides the CURLOPTCERTINFO option to allow applications to request details to be returned about a TLS server's certificate chain. Due to an erroneous function, a malicious server could make libcurl built with NSS get stuck in a never-ending busy-loop when trying to retrieve that...

NTLM type-2 out-of-bounds buffer read

libcurl contains a heap buffer out-of-bounds read flaw. The function handling incoming NTLM type-2 messages lib/vauth/ntlm.c:ntlmdecodetype2target does not validate incoming data correctly and is subject to an integer overflow vulnerability. Using that overflow, a malicious or broken NTLM server...

NTLM password overflow via integer overflow

libcurl contains a buffer overrun in the NTLM authentication code. The internal function Curlntlmcoremknthash multiplies the length of the password by two SUM to figure out how large temporary storage area to allocate from the heap. The length value is then subsequently used to iterate over the...

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...

case insensitive password comparison

When reusing a connection, curl was doing case insensitive comparisons of username and password with the existing connections. This means that if an unused connection with proper credentials exists for a protocol that has connection-scoped credentials, an attacker can cause that connection to be...

URL unescape heap overflow via integer truncation

The URL percent-encoding decode function in libcurl is called curleasyunescape. Internally, even if this function would be made to allocate a destination buffer larger than 2GB, it would return that new length in a signed 32-bit integer variable, thus the length would get either truncated only or...

cookie leak with IP address as domain

By not detecting and rejecting domain names for partial literal IP addresses properly when parsing received HTTP cookies, libcurl can be fooled to both sending cookies to wrong sites and into allowing arbitrary sites to set cookies for others. For this problem to trigger, the client application...

URL sanitization vulnerability

curl is vulnerable to a data injection attack for certain protocols through control characters embedded or percent-encoded in URLs. When parsing URLs, libcurl's parser is liberal and only parses as little as possible and lets as much as possible through as long as it can figure out what to do. In...

SSL CBC IV vulnerability

curl is vulnerable to a SSL CBC IV vulnerability when built to use OpenSSL for the SSL/TLS layer. This vulnerability has been identified CVE-2011-3389 aka the "BEAST" attack and is addressed by OpenSSL already as they have made a workaround to mitigate the problem. When doing so, they figured out...

data callback excessive length

When downloading data, libcurl hands it over to the application using a callback that is registered by the client software. libcurl then calls that function repeatedly with data until the transfer is complete. The callback is documented to receive a maximum data size of 16K CURLMAXWRITESIZE. Usin...

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...

HSTS long filename clears contents

When saving HSTS data to an excessively long filename, curl could end up removing all contents, making subsequent requests using that file unaware of the HSTS status they should otherwise use...

cookie mixed case PSL bypass

This flaw allows a malicious HTTP server to set "super cookies" in curl that are then passed back to more origins than what is otherwise allowed or possible. This allows a site to set cookies that then would get sent to different and unrelated sites and domains. It could do this by exploiting a...

cookie injection with none file

This flaw allows an attacker to intentionally inject cookies into a running program using libcurl, if the specific series of conditions are met. libcurl performs transfers. In its API, an application creates "easy handles" that are the individual handles for single transfers. libcurl provides 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...

GSS delegation too eager connection reuse

libcurl would reuse a previously created connection even when the GSS delegation CURLOPTGSSAPIDELEGATION option had been changed that could have changed the user's permissions in a second transfer. libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if...

OAUTH2 bearer bypass in connection reuse

libcurl might 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 protocols: SMTPS, IMAPS, POP3S and LDAPS OpenLDAP only. libcurl maintains a pool of live connection...

Auth/cookie leak on redirect

curl might leak authentication or cookie header data on HTTP redirects to the same host but another port number. When asked to send custom headers or cookies in its HTTP requests, curl sends that set of headers only to the host which name is used in the initial URL, so that redirects to other hos...

invalid URL parsing with '#'

curl does not parse the authority component of the URL correctly when the host name part ends with a hash character, and could instead be tricked into connecting to a different host. This may have security implications if you for example use a URL parser that follows the RFC to check for allowed...

IDNA 2003 makes curl use wrong host

When curl is built with libidn to handle International Domain Names IDNA, it translates them to puny code for DNS resolving using the IDNA 2003 standard, while IDNA 2008 is the modern and up-to-date IDNA standard. This misalignment causes problems with for example domains using the German ß...

double free in krb5 code

In curl's implementation of the Kerberos authentication mechanism, the function readdata in security.c is used to fill the necessary krb5 structures. When reading one of the length fields from the socket, it fails to ensure that the length parameter passed to realloc is not set to 0. This would...

wrong reuse of connections

libcurl can in some circumstances reuse the wrong connection when asked to do transfers using other protocols than HTTP and FTP. 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...

cookie domain tailmatch

libcurl is vulnerable to a cookie leak vulnerability when doing requests across domains with matching tails. When communicating over HTTPS and having libcurl's cookie engine enabled, libcurl stores and holds cookies for use when subsequent requests are done to hosts and paths that match those kep...

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...

FTP too eager connection reuse

libcurl would reuse a previously created FTP connection even when one or more options had been changed that could have made the effective user a different one, thus leading to doing the second transfer with the wrong credentials. libcurl keeps previously used connections in a connection pool for...

TELNET option IAC injection

curl supports communicating using the TELNET protocol and as a part of this it offers users to pass on username and "telnet options" for the server negotiation. Due to lack of proper input scrubbing and without it being the documented functionality, curl would pass on username and telnet options ...

.netrc parser out-of-bounds access

curl can be told to parse a .netrc file for credentials. If that file ends in a line with consecutive non-white space letters and no newline, curl could read past the end of the stack-based buffer, and if the read works, write a zero byte possibly beyond its boundary. This does in most cases caus...

FTP-KRB bad message verification

When curl 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...

percent-encoded path separator in URL host

The curl URL parser wrongly accepts percent-encoded URL separators like '/' when decoding the hostname part of a URL, making it a different URL using the wrong hostname when it is later retrieved. For example, a URL like http://example.com%2F10.0.0.1/, would be allowed by the parser and get...

HSTS bypass via trailing dot

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 directly instead of using an insecure clear-text HTTP step even when HTTP is provided in the URL. This mechanism could be bypassed if the hostname in the given URL used ...