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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT Security Bulletin ASB-2016.0101 Multiple vulnerabilities have been identified in cURL 3 November 2016 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: cuRL Operating System: UNIX variants (UNIX, Linux, OSX) Windows Impact/Access: Execute Arbitrary Code/Commands -- Remote/Unauthenticated Denial of Service -- Remote/Unauthenticated Provide Misleading Information -- Remote/Unauthenticated Access Confidential Data -- Remote/Unauthenticated Unauthorised Access -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2016-8625 CVE-2016-8624 CVE-2016-8623 CVE-2016-8622 CVE-2016-8621 CVE-2016-8620 CVE-2016-8619 CVE-2016-8618 CVE-2016-8617 CVE-2016-8616 CVE-2016-8615 Member content until: Saturday, December 3 2016 OVERVIEW Multiple vulnerabilities have been identified in cURL prior to version 7.51.0. [1] IMPACT The following details have been provided regarding the vulnerabilities: CVE-2016-8615: "If cookie state is written into a cookie jar file that is later read back and used for subsequent requests, a malicious HTTP server can inject new cookies for arbitrary domains into said cookie jar. The issue pertains to the function that loads cookies into memory, which reads the specified file into a fixed-size buffer in a line-by-line manner using the fgets() function. If an invocation of fgets() cannot read the whole line into the destination buffer due to it being too small, it truncates the output. This way, a very long cookie (name + value) sent by a malicious server would be stored in the file and subsequently that cookie could be read partially and crafted correctly, it could be treated as a different cookie for another server." [2] CVE-2016-8616: "When re-using a connection, curl was doing case insensitive comparisons of user name 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 reused if s/he knows the case-insensitive version of the correct password." [3] CVE-2016-8617: "On systems with 32-bit addresses in userspace (e.g. x86, ARM, x32), the multiplication in the expression wraps around if insize is at least 1GB of data. If this happens, an undersized output buffer will be allocated, but the full result will be written, thus causing the memory behind the output buffer to be overwritten. If a username is set directly via CURLOPT_USERNAME (or curl's -u, --user option), this vulnerability can be triggered. The name has to be at least 512MB big in a 32bit system." [4] CVE-2016-8618: "The libcurl API function called curl_maprintf() can be tricked into doing a double-free due to an unsafe size_t multiplication, on systems using 32 bit size_t variables. The function is also used internallty in numerous situations. The function doubles an allocated memory area with realloc() and allows the size to wrap and become zero and when doing so realloc() returns NULL and frees the memory - in contrary to normal realloc() fails where it only returns NULL - causing libcurl to free the memory again in the error path. Systems with 64 bit versions of the size_t type are not affected by this issue." [5] CVE-2016-8619: "In curl's implementation of the Kerberos authentication mechanism, the function read_data() 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 lead to realloc() getting called with a zero size and when doing so realloc() returns NULL and frees the memory - in contrary to normal realloc() fails where it only returns NULL - causing libcurl to free the memory again in the error path. This flaw could be triggered by a malicious or just otherwise ill-behaving server." [6] CVE-2016-8620: "The curl tool's "globbing" feature allows a user to specify a numerical range through which curl will iterate. It is typically specified as [1-5], specifying the first and the last numbers in the range. Or with [a-z], using letters. The curl code for parsing the second unsigned number did not check for a leading minus character, which allowed a user to specify [1--1] with no complaints and have the latter -1 number get turned into the largest unsigned long value the system can handle. This would ultimately cause curl to write outside the dedicated malloced buffer after no less than 100,000 iterations, since it would have room for 5 digits but not 6. When the range is specified with letters, and the ending letter is left out [L-], the code would still advance its read pointer 5 bytes even if the string was just 4 bytes and end up reading outside the given buffer." [7] CVE-2016-8621: "The curl_getdate converts a given date string into a numerical timestamp and it supports a range of different formats and possibilites 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 servers) and it can be used when doing conditional HTTP requests. The date parser function uses the libc sscanf() function at two places, with the parsing strings "%02d:%02d" and ""%02d:%02d:%02d". The intent being that it would parse either a string with HH:MM (two digits colon two digits) or HH:MM:SS (two digits colon two digits colon two digits). If instead the piece of time that was sent in had the final digit cut off, thus ending with a single-digit, the date parser code would advance its read pointer one byte too much and end up reading out of bounds." [8] CVE-2016-8622: "The URL percent-encoding decode function in libcurl is called curl_easy_unescape. Internally, even if this function would be made to allocate a unscape destination buffer larger than 2GB, it would return that new length in a signed 32 bit integer variable, thus the length would get either just truncated or both truncated and turned negative. That could then lead to libcurl writing outside of its heap based buffer. This can be triggered by a user on a 64bit system if the user can send in a custom (very large) URL to a libcurl using program." [9] CVE-2016-8623: "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 funcion however only returns a list with references back to the original strings for name, value, path and so on. Therefore, if another thread quickly takes the lock and frees one of the original cookie structs together with its strings, a use-after-free can occur and lead to information disclosure. Another thread can also replace the contents of the cookies from separate HTTP responses or API calls." [10] CVE-2016-8624: "curl doesn't parse the authority component of the URL correctly when the host name part ends with a '#' 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 domains before using curl to request them. Passing in http://example.com#@evil.com/x.txt would wrongly make curl send a request to evil.com while your browser would connect to example.com given the same URL. The problem exists for most protocol schemes." [11] CVE-2016-8625: "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 B character (known as the Unicode Character 'LATIN SMALL LETTER SHARP S') which is used at times in the .de TLD and is translated differently in the two IDNA standards, leading to users potentially and unknowingly issuing network transfer requests to the wrong host. For example, straBe.de is translated into strasse.de using IDNA 2003 but is translated into xn--strae-oqa.de using IDNA 2008. Needless to say, those host names could very well resolve to different addresses and be two completely independent servers. IDNA 2008 is mandatory for .de domains. curl is not alone with this problem, as there's currently a big flux in the world of network user-agents about which IDNA version to support and use. This name problem exists for DNS-using protocols in curl, but only when built to use libidn." [12] MITIGATION Users are advised to upgrade to the latest version to address these issues. [1] REFERENCES [1] cURL -- multiple vulnerabilities https://www.vuxml.org/freebsd/765feb7d-a0d1-11e6-a881-b499baebfeaf.html [2] cookie injection for other servers https://curl.haxx.se/docs/adv_20161102A.html [3] case insensitive password comparison https://curl.haxx.se/docs/adv_20161102B.html [4] OOB write via unchecked multiplication https://curl.haxx.se/docs/adv_20161102C.html [5] double-free in curl_maprintf https://curl.haxx.se/docs/adv_20161102D.html [6] double-free in krb5 code https://curl.haxx.se/docs/adv_20161102E.html [7] glob parser write/read out of bounds https://curl.haxx.se/docs/adv_20161102F.html [8] curl_getdate read out of bounds https://curl.haxx.se/docs/adv_20161102G.html [9] URL unescape heap overflow via integer truncation https://curl.haxx.se/docs/adv_20161102H.html [10] Use-after-free via shared cookies https://curl.haxx.se/docs/adv_20161102I.html [11] invalid URL parsing with '#' https://curl.haxx.se/docs/adv_20161102J.html [12] IDNA 2003 makes curl use wrong host https://curl.haxx.se/docs/adv_20161102K.html AusCERT has made every effort to ensure that the information contained in this document is accurate. However, the decision to use the information described is the responsibility of each user or organisation. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). 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