From: The FreeBSD Project Bug: https://security-tracker.debian.org/tracker/CVE-2014-9862 Subject: CVE-2014-9862 - check for a negative value on numbers of bytes The implementation of bspatch does not check for a negative value on numbers of bytes read from the diff and extra streams, allowing an attacker who can control the patch file to write at arbitrary locations in the heap. . bspatch's main loop reads three numbers from the "control" stream in the patch: X, Y and Z. The first two are the number of bytes to read from "diff" and "extra" (and thus only non-negative), while the third one could be positive or negative and moves the oldpos pointer on the source image. These 3 values are 64bits signed ints (encoded somehow on the file) that are later passed the function that reads from the streams, but those values are not verified to be non-negative. . Official report https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-9862 The patch was downloaded from a link pointed by https://security.freebsd.org/advisories/FreeBSD-SA-16:25.bsp --- bspatch.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/bspatch.c +++ b/bspatch.c @@ -152,6 +152,10 @@ int main(int argc,char * argv[]) }; /* Sanity-check */ + if ((ctrl[0] < 0) || (ctrl[1] < 0)) + errx(1,"Corrupt patch\n"); + + /* Sanity-check */ if(newpos+ctrl[0]>newsize) errx(1,"Corrupt patch\n");