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From: Jonas Meurer <jonas@freesources.org>
Date: Tue, 11 Jun 2019 12:16:46 +0200
Subject: Fix #501: Uninitialized read in gdImageCreateFromXbm
(CVE-2019-11038)
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2019-11038
Bug-Debian: https://bugs.debian.org/929821
Bug: https://github.com/libgd/libgd/issues/501
We have to ensure that `sscanf()` does indeed read a hex value here,
and bail out otherwise.
Original patch by Christoph M. Becker <cmbecker69@gmx.de> for PHP libgd ext.
https://git.php.net/?p=php-src.git;a=commit;h=ed6dee9a198c904ad5e03113e58a2d2c200f5184
---
src/gd_xbm.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/src/gd_xbm.c b/src/gd_xbm.c
index 5f09b56..9d6dd20 100644
--- a/src/gd_xbm.c
+++ b/src/gd_xbm.c
@@ -166,7 +166,11 @@ BGD_DECLARE(gdImagePtr) gdImageCreateFromXbm(FILE * fd)
}
h[3] = ch;
}
- sscanf(h, "%x", &b);
+ if (sscanf(h, "%x", &b) != 1) {
+ gd_error("invalid XBM");
+ gdImageDestroy(im);
+ return 0;
+ }
for (bit = 1; bit <= max_bit; bit = bit << 1) {
gdImageSetPixel(im, x++, y, (b & bit) ? 1 : 0);
if (x == im->sx) {
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