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package/sudo: backport patch CVE-2026-35535

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This backport is provided thanks to the Debian community [1].

- CVE-2026-35535:
    In Sudo through 1.9.17p2 before 3e474c2, a failure of a setuid,
    setgid, or setgroups call, during a privilege drop before running the
    mailer, is not a fatal error and can lead to privilege escalation.

For more information, see:
    https://www.cve.org/CVERecord?id=CVE-2026-35535

[1] https://salsa.debian.org/sudo-team/sudo/-/blob/debian/trixie/debian/patches/0006-exec_mailer-Set-group-as-well-as-uid-when-running-th.patch

Signed-off-by: Thomas Perale <thomas.perale@mind.be>
Signed-off-by: Fiona Klute <fiona.klute@gmx.de>
This commit is contained in:
Thomas Perale
2026-06-26 22:45:20 +02:00
committed by Fiona Klute
parent 353007cf40
commit 54de8d26d0
2 changed files with 151 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

147
package/sudo/0001-exec-mailer-set-group-as-well-as-uid-when-running-the-mailer.patch Normal file
View File

@@ -0,0 +1,147 @@
From 3e474c2f201484be83d994ae10a4e20e8c81bb69 Mon Sep 17 00:00:00 2001
From: "Todd C. Miller" <Todd.Miller@sudo.ws>
Date: Sat, 8 Nov 2025 15:34:02 -0700
Subject: [PATCH] exec_mailer: Set group as well as uid when running the mailer
Also make a setuid(), setgid() or setgroups() failure fatal.
Found by the ZeroPath AI Security Engineer <https://zeropath.com>
CVE: CVE-2026-35535
Upstream: https://github.com/sudo-project/sudo/commit/3e474c2f201484be83d994ae10a4e20e8c81bb69
Signed-off-by: Thomas Perale <thomas.perale@mind.be>
---
include/sudo_eventlog.h | 3 ++-
lib/eventlog/eventlog.c | 21 +++++++++++++++++----
lib/eventlog/eventlog_conf.c | 4 +++-
plugins/sudoers/logging.c | 2 +-
plugins/sudoers/policy.c | 2 +-
5 files changed, 24 insertions(+), 8 deletions(-)
diff --git a/include/sudo_eventlog.h b/include/sudo_eventlog.h
index eb9f4f4..485d259 100644
--- a/include/sudo_eventlog.h
+++ b/include/sudo_eventlog.h
@@ -80,6 +80,7 @@ struct eventlog_config {
int syslog_rejectpri;
int syslog_alertpri;
uid_t mailuid;
+ gid_t mailgid;
bool omit_hostname;
const char *logpath;
const char *time_fmt;
@@ -151,7 +152,7 @@ void eventlog_set_syslog_rejectpri(int pri);
void eventlog_set_syslog_alertpri(int pri);
void eventlog_set_syslog_maxlen(size_t len);
void eventlog_set_file_maxlen(size_t len);
-void eventlog_set_mailuid(uid_t uid);
+void eventlog_set_mailuser(uid_t uid, gid_t gid);
void eventlog_set_omit_hostname(bool omit_hostname);
void eventlog_set_logpath(const char *path);
void eventlog_set_time_fmt(const char *fmt);
diff --git a/lib/eventlog/eventlog.c b/lib/eventlog/eventlog.c
index 5a32824..d56c4e4 100644
--- a/lib/eventlog/eventlog.c
+++ b/lib/eventlog/eventlog.c
@@ -304,15 +304,13 @@ exec_mailer(int pipein)
syslog(LOG_ERR, _("unable to dup stdin: %m")); // -V618
sudo_debug_printf(SUDO_DEBUG_ERROR,
"unable to dup stdin: %s", strerror(errno));
- sudo_debug_exit(__func__, __FILE__, __LINE__, sudo_debug_subsys);
- _exit(127);
+ goto bad;
}
/* Build up an argv based on the mailer path and flags */
if ((mflags = strdup(evl_conf->mailerflags)) == NULL) {
syslog(LOG_ERR, _("unable to allocate memory")); // -V618
- sudo_debug_exit(__func__, __FILE__, __LINE__, sudo_debug_subsys);
- _exit(127);
+ goto bad;
}
argv[0] = sudo_basename(mpath);
@@ -331,11 +329,23 @@ exec_mailer(int pipein)
if (setuid(ROOT_UID) != 0) {
sudo_debug_printf(SUDO_DEBUG_ERROR, "unable to change uid to %u",
ROOT_UID);
+ goto bad;
+ }
+ if (setgid(evl_conf->mailgid) != 0) {
+ sudo_debug_printf(SUDO_DEBUG_ERROR, "unable to change gid to %u",
+ (unsigned int)evl_conf->mailgid);
+ goto bad;
+ }
+ if (setgroups(1, &evl_conf->mailgid) != 0) {
+ sudo_debug_printf(SUDO_DEBUG_ERROR, "unable to set groups to %u",
+ (unsigned int)evl_conf->mailgid);
+ goto bad;
}
if (evl_conf->mailuid != ROOT_UID) {
if (setuid(evl_conf->mailuid) != 0) {
sudo_debug_printf(SUDO_DEBUG_ERROR, "unable to change uid to %u",
(unsigned int)evl_conf->mailuid);
+ goto bad;
}
}
sudo_debug_exit(__func__, __FILE__, __LINE__, sudo_debug_subsys);
@@ -347,6 +357,9 @@ exec_mailer(int pipein)
sudo_debug_printf(SUDO_DEBUG_ERROR, "unable to execute %s: %s",
mpath, strerror(errno));
_exit(127);
+bad:
+ sudo_debug_exit(__func__, __FILE__, __LINE__, sudo_debug_subsys);
+ _exit(127);
}
/* Send a message to the mailto user */
diff --git a/lib/eventlog/eventlog_conf.c b/lib/eventlog/eventlog_conf.c
index 0663a38..ec3b569 100644
--- a/lib/eventlog/eventlog_conf.c
+++ b/lib/eventlog/eventlog_conf.c
@@ -70,6 +70,7 @@ static struct eventlog_config evl_conf = {
MAXSYSLOGLEN, /* syslog_maxlen */
0, /* file_maxlen */
ROOT_UID, /* mailuid */
+ ROOT_GID, /* mailgid */
false, /* omit_hostname */
_PATH_SUDO_LOGFILE, /* logpath */
"%h %e %T", /* time_fmt */
@@ -151,9 +152,10 @@ eventlog_set_file_maxlen(size_t len)
}
void
-eventlog_set_mailuid(uid_t uid)
+eventlog_set_mailuser(uid_t uid, gid_t gid)
{
evl_conf.mailuid = uid;
+ evl_conf.mailgid = gid;
}
void
diff --git a/plugins/sudoers/logging.c b/plugins/sudoers/logging.c
index bd4de92..9535289 100644
--- a/plugins/sudoers/logging.c
+++ b/plugins/sudoers/logging.c
@@ -1157,7 +1157,7 @@ init_eventlog_config(void)
eventlog_set_syslog_alertpri(def_syslog_badpri);
eventlog_set_syslog_maxlen(def_syslog_maxlen);
eventlog_set_file_maxlen(def_loglinelen);
- eventlog_set_mailuid(ROOT_UID);
+ eventlog_set_mailuser(ROOT_UID, ROOT_GID);
eventlog_set_omit_hostname(!def_log_host);
eventlog_set_logpath(def_logfile);
eventlog_set_time_fmt(def_log_year ? "%h %e %T %Y" : "%h %e %T");
diff --git a/plugins/sudoers/policy.c b/plugins/sudoers/policy.c
index f3adfb0..27f6e58 100644
--- a/plugins/sudoers/policy.c
+++ b/plugins/sudoers/policy.c
@@ -639,7 +639,7 @@ sudoers_policy_deserialize_info(struct sudoers_context *ctx, void *v,
}
#ifdef NO_ROOT_MAILER
- eventlog_set_mailuid(ctx->user.uid);
+ eventlog_set_mailuser(ctx->user.uid, ctx->user.gid);
#endif
/* Dump settings and user info (XXX - plugin args) */

4
package/sudo/sudo.mk
View File

@@ -12,6 +12,10 @@ SUDO_LICENSE = ISC, BSD-3-Clause
SUDO_LICENSE_FILES = LICENSE.md
SUDO_CPE_ID_VERSION = $(SUDO_VERSION_MAJOR)
SUDO_CPE_ID_UPDATE = $(SUDO_VERSION_MINOR)
# 0001-exec-mailer-set-group-as-well-as-uid-when-running-the-mailer.patch
SUDO_IGNORE_CVES += CVE-2026-35535
SUDO_SELINUX_MODULES = sudo
# This is to avoid sudo's make install from chown()ing files which fails
SUDO_INSTALL_TARGET_OPTS = INSTALL_OWNER="" DESTDIR="$(TARGET_DIR)" install