From 9cd6d7efb87d6d51a9ddce152d103ac087287c52 Mon Sep 17 00:00:00 2001 From: Olivier Fourdan Date: Mon, 28 Apr 2025 10:46:03 +0200 Subject: [PATCH xserver 4/6] os: Account for bytes to ignore when sharing input buffer When reading requests from the clients, the input buffer might be shared and used between different clients. If a given client sends a full request with non-zero bytes to ignore, the bytes to ignore may still be non-zero even though the request is full, in which case the buffer could be shared with another client who's request will not be processed because of those bytes to ignore, leading to a possible hang of the other client request. To avoid the issue, make sure we have zero bytes to ignore left in the input request when sharing the input buffer with another client. CVE-2025-49178 This issue was discovered by Nils Emmerich and reported by Julian Suleder via ERNW Vulnerability Disclosure. Signed-off-by: Olivier Fourdan Reviewed-by: Peter Hutterer (cherry picked from commit b0c1cbf4f8e6baa372b1676d2f30512de8ab4ed3) --- os/io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/os/io.c b/os/io.c index 064d69ea3..83986af92 100644 --- a/os/io.c +++ b/os/io.c @@ -444,7 +444,7 @@ ReadRequestFromClient(ClientPtr client) */ gotnow -= needed; - if (!gotnow) + if (!gotnow && !oci->ignoreBytes) AvailableInput = oc; if (move_header) { if (client->req_len < bytes_to_int32(sizeof(xBigReq) - sizeof(xReq))) { -- 2.49.0