From: Stephan Bosch <stephan.bosch@open-xchange.com>
Date: Sun, 29 Mar 2026 18:03:40 +0000 (+0200)
Subject: imap: cmd-append - Fix assertion panic occurring upon invalid 'REPLACE 0' command
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=HEAD;p=thirdparty%2Fdovecot%2Fcore.git

imap: cmd-append - Fix assertion panic occurring upon invalid 'REPLACE 0' command

Panic was:
Panic: file mail-cache-lookup.c: line 354 (mail_cache_field_exists): assertion failed: (seq > 0)
---

diff --git a/src/imap/cmd-append.c b/src/imap/cmd-append.c
index cf1ca6cd8e..f5fc0eb666 100644
--- a/src/imap/cmd-append.c
+++ b/src/imap/cmd-append.c
@@ -1159,7 +1159,8 @@ static bool cmd_append_full(struct client_command_context *cmd, bool replace)
 	ctx->started = ioloop_time;
 	ctx->utf8_accept = (client_enabled_mailbox_features(cmd->client) &
 			    MAILBOX_FEATURE_UTF8ACCEPT) != 0;
-	if (replace && !cmd->uid && (seqnum > client->messages_count)) {
+	if (replace && !cmd->uid &&
+	    (seqnum == 0 || seqnum > client->messages_count)) {
 		client_send_tagline(cmd,
 			"BAD Invalid message sequence.");
 		ctx->failed = TRUE;