Date: Wed, 29 Apr 2026 14:47:47 +0000 From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 2621f6c5d4ae - stable/15 - dhclient: Check for unexpected characters in some DHCP server options Message-ID: <69f21a13.3b7c4.286ada73@gitrepo.freebsd.org>
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The branch stable/15 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=2621f6c5d4aeb0cef12aab812431a1581b384e06 commit 2621f6c5d4aeb0cef12aab812431a1581b384e06 Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2026-04-27 20:03:09 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2026-04-29 14:40:57 +0000 dhclient: Check for unexpected characters in some DHCP server options Some options are written directly to the lease file, which may be parsed by subsequent dhclient invocations. We must make sure that a malicious server can't control the "medium" field of a lease definition, otherwise they can achieve RCE by injecting one into the lease file, whereupon it will be passed to dhclient-script, which passes it through eval. Approved by: so Security: FreeBSD-SA-26:12.dhclient Security: CVE-2026-42511 Reported by: Joshua Rogers of AISLE Research Team (https://aisle.com/) --- sbin/dhclient/dhclient.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/sbin/dhclient/dhclient.c b/sbin/dhclient/dhclient.c index 5d2a7453578b..719e20cffad9 100644 --- a/sbin/dhclient/dhclient.c +++ b/sbin/dhclient/dhclient.c @@ -1226,6 +1226,12 @@ packet_to_lease(struct packet *packet) } memcpy(lease->server_name, packet->raw->sname, DHCP_SNAME_LEN); lease->server_name[DHCP_SNAME_LEN]='\0'; + if (strchr(lease->server_name, '"') != NULL || + strchr(lease->server_name, '\\') != NULL) { + warning("dhcpoffer: server name contains invalid characters."); + free_client_lease(lease); + return (NULL); + } } /* Ditto for the filename. */ @@ -1241,6 +1247,12 @@ packet_to_lease(struct packet *packet) } memcpy(lease->filename, packet->raw->file, DHCP_FILE_LEN); lease->filename[DHCP_FILE_LEN]='\0'; + if (strchr(lease->filename, '"') != NULL || + strchr(lease->filename, '\\') != NULL) { + warning("dhcpoffer: filename contains invalid characters."); + free_client_lease(lease); + return (NULL); + } } return lease; }home | help
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