From 54928cb9eaa7143ff17f463efa7ed3109afdbf30 Mon Sep 17 00:00:00 2001
From: "djm@openbsd.org" <djm@openbsd.org>
Date: Thu, 4 Sep 2025 00:30:06 +0000
Subject: [PATCH] upstream: don't allow \0 characters in url-encoded strings.
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Suggested by David Leadbeater, ok deraadt@

OpenBSD-Commit-ID: c92196cef0f970ceabc1e8007a80b01e9b7cd49c

Upstream-Status: Backport [Upstream commit https://github.com/openssh/openssh-portable/commit/43b3bff47bb029f2299bacb6a36057981b39fdb0]
CVE: CVE-2025-61985
Signed-off-by: David Nyström <david.nystrom@est.tech>
---
 misc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/misc.c b/misc.c
index 3db2e4d0b..cac246b63 100644
--- a/misc.c
+++ b/misc.c
@@ -955,7 +955,7 @@ urldecode(const char *src)
 	size_t srclen;
 
 	if ((srclen = strlen(src)) >= SIZE_MAX)
-		fatal_f("input too large");
+		return NULL;
 	ret = xmalloc(srclen + 1);
 	for (dst = ret; *src != '\0'; src++) {
 		switch (*src) {
@@ -963,9 +963,10 @@ urldecode(const char *src)
 			*dst++ = ' ';
 			break;
 		case '%':
+			/* note: don't allow \0 characters */
 			if (!isxdigit((unsigned char)src[1]) ||
 			    !isxdigit((unsigned char)src[2]) ||
-			    (ch = hexchar(src + 1)) == -1) {
+			    (ch = hexchar(src + 1)) == -1 || ch == 0) {
 				free(ret);
 				return NULL;
 			}
-- 
2.44.1

