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FreeBSD : cURL library -- heap corruption in curl_easy_unescape (01cf67b3-dc3b-11e2-a6cd-c48508086173)
medium Nessus Plugin ID 66968
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Synopsis
The remote FreeBSD host is missing a security-related update.Description
cURL developers report :libcurl is vulnerable to a case of bad checking of the input data which may lead to heap corruption.
The function curl_easy_unescape() 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 string is written to an allocated memory area that the function returns to the caller.
The function takes a source string and a length parameter, and if the length provided is 0 the function will instead use strlen() to figure out how much data to parse.
The '%HH' parser wrongly only considered the case where a zero byte would terminate the input. If a length-limited buffer was passed in which ended with a '%' character which was followed by two hexadecimal digits outside of the buffer libcurl was allowed to parse alas without a terminating zero, libcurl would still parse that sequence as well.
The counter for remaining data to handle would then be decreased too much and wrap to become a very large integer and the copying would go on too long and the destination buffer that is allocated on the heap would get overwritten.
We consider it unlikely that programs allow user-provided strings unfiltered into this function. Also, only the not zero-terminated input string use case is affected by this flaw. Exploiting this flaw for gain is probably possible for specific circumstances but we consider the general risk for this to be low.
The curl command line tool is not affected by this problem as it doesn't use this function.
There are no known exploits available at this time.
Solution
Update the affected package.See Also
Plugin Details
Severity: Medium
ID: 66968
File Name: freebsd_pkg_01cf67b3dc3b11e2a6cdc48508086173.nasl
Version: 1.7
Type: local
Family: FreeBSD Local Security Checks
Published: 6/24/2013
Updated: 1/6/2021
Supported Sensors: Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 6.7
CVSS v2
Risk Factor: Medium
Base Score: 6.8
Vector: CVSS2#AV:N/AC:M/Au:N/C:P/I:P/A:P
Vulnerability Information
CPE: p-cpe:/a:freebsd:freebsd:curl, cpe:/o:freebsd:freebsd
Required KB Items: Host/local_checks_enabled, Host/FreeBSD/release, Host/FreeBSD/pkg_info
Patch Publication Date: 6/23/2013
Vulnerability Publication Date: 6/22/2013
Reference Information
CVE: CVE-2013-2174