From 258128aefef95cae78cb5fba8572dc6ce285c801 Mon Sep 17 00:00:00 2001 From: Thomas Perale Date: Tue, 12 May 2026 10:10:41 +0200 Subject: [PATCH] package/libvncserver: patch CVE-2026-3285{3, 4} MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit - CVE-2026-32853: LibVNCServer versions 0.9.15 and prior (fixed in commit 009008e) contain a heap out-of-bounds read vulnerability in the UltraZip encoding handler that allows a malicious VNC server to cause information disclosure or application crash. Attackers can exploit improper bounds checking in the HandleUltraZipBPP() function by manipulating subrectangle header counts to read beyond the allocated heap buffer. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2026-32853 - https://github.com/LibVNC/libvncserver/security/advisories/GHSA-87q7-v983-qwcj - https://github.com/LibVNC/libvncserver/commit/009008e2f4d5a54dd71f422070df3af7b3dbc931 - CVE-2026-32854: LibVNCServer versions 0.9.15 and prior (fixed in commit dc78dee) contain null pointer dereference vulnerabilities in the HTTP proxy handlers within httpProcessInput() in httpd.c that allow remote attackers to cause a denial of service by sending specially crafted HTTP requests. Attackers can exploit missing validation of strchr() return values in the CONNECT and GET proxy handling paths to trigger null pointer dereferences and crash the server when httpd and proxy features are enabled. For more information, see: - https://www.cve.org/CVERecord?id=CVE-2026-32854 - https://github.com/LibVNC/libvncserver/security/advisories/GHSA-xjp8-4qqv-5x4x - https://github.com/LibVNC/libvncserver/commit/dc78dee51a7e270e537a541a17befdf2073f5314 Signed-off-by: Thomas Perale Signed-off-by: Julien Olivain --- ...cks-to-UltraZip-subrectangle-parsing.patch | 74 +++++++++++++++++++ ...dereferences-in-httpd-proxy-handlers.patch | 64 ++++++++++++++++ package/libvncserver/libvncserver.mk | 6 ++ 3 files changed, 144 insertions(+) create mode 100644 package/libvncserver/0002-add-bounds-checks-to-UltraZip-subrectangle-parsing.patch create mode 100644 package/libvncserver/0003-fix-NULL-pointer-dereferences-in-httpd-proxy-handlers.patch diff --git a/package/libvncserver/0002-add-bounds-checks-to-UltraZip-subrectangle-parsing.patch b/package/libvncserver/0002-add-bounds-checks-to-UltraZip-subrectangle-parsing.patch new file mode 100644 index 0000000000..fa4a7718cc --- /dev/null +++ b/package/libvncserver/0002-add-bounds-checks-to-UltraZip-subrectangle-parsing.patch @@ -0,0 +1,74 @@ +From 009008e2f4d5a54dd71f422070df3af7b3dbc931 Mon Sep 17 00:00:00 2001 +From: Kazuma Matsumoto <269371721+y637F9QQ2x@users.noreply.github.com> +Date: Sun, 22 Mar 2026 20:35:49 +0100 +Subject: [PATCH] libvncclient: add bounds checks to UltraZip subrectangle + parsing + +HandleUltraZipBPP() iterates over sub-rectangles using numCacheRects +(derived from the attacker-controlled rect.r.x) without validating +that the pointer stays within the decompressed data buffer. A malicious +server can set a large numCacheRects value, causing heap out-of-bounds +reads via the memcpy calls in the parsing loop. + +Add bounds checks before reading the 12-byte subrect header and before +advancing the pointer by the raw pixel data size. Use uint64_t for the +raw data size calculation to prevent integer overflow on 32-bit platforms. + +Upstream: https://github.com/LibVNC/libvncserver/commit/009008e2f4d5a54dd71f422070df3af7b3dbc931 +CVE: CVE-2026-32853 +Signed-off-by: Thomas Perale +--- + src/libvncclient/ultra.c | 16 +++++++++++++++- + 1 file changed, 15 insertions(+), 1 deletion(-) + +diff --git a/src/libvncclient/ultra.c b/src/libvncclient/ultra.c +index 1d3aaba6a..5633b8cbb 100644 +--- a/src/libvncclient/ultra.c ++++ b/src/libvncclient/ultra.c +@@ -126,6 +126,7 @@ HandleUltraZipBPP (rfbClient* client, int rx, int ry, int rw, int rh) + int toRead=0; + int inflateResult=0; + unsigned char *ptr=NULL; ++ unsigned char *ptr_end=NULL; + lzo_uint uncompressedBytes = ry + (rw * 65535); + unsigned int numCacheRects = rx; + +@@ -194,11 +195,18 @@ HandleUltraZipBPP (rfbClient* client, int rx, int ry, int rw, int rh) + + /* Put the uncompressed contents of the update on the screen. */ + ptr = (unsigned char *)client->raw_buffer; ++ ptr_end = ptr + uncompressedBytes; + for (i=0; i ptr_end) { ++ rfbClientLog("UltraZip: subrect %d header exceeds decompressed data bounds\n", i); ++ return FALSE; ++ } ++ + memcpy((char *)&sx, ptr, 2); ptr += 2; + memcpy((char *)&sy, ptr, 2); ptr += 2; + memcpy((char *)&sw, ptr, 2); ptr += 2; +@@ -213,8 +221,13 @@ HandleUltraZipBPP (rfbClient* client, int rx, int ry, int rw, int rh) + + if (se == rfbEncodingRaw) + { ++ uint64_t rawBytes = (uint64_t)sw * sh * (BPP / 8); ++ if (rawBytes > (size_t)(ptr_end - ptr)) { ++ rfbClientLog("UltraZip: subrect %d raw data exceeds decompressed data bounds\n", i); ++ return FALSE; ++ } + client->GotBitmap(client, (unsigned char *)ptr, sx, sy, sw, sh); +- ptr += ((sw * sh) * (BPP / 8)); ++ ptr += (size_t)rawBytes; + } + } + +@@ -222,3 +235,4 @@ HandleUltraZipBPP (rfbClient* client, int rx, int ry, int rw, int rh) + } + + #undef CARDBPP ++ diff --git a/package/libvncserver/0003-fix-NULL-pointer-dereferences-in-httpd-proxy-handlers.patch b/package/libvncserver/0003-fix-NULL-pointer-dereferences-in-httpd-proxy-handlers.patch new file mode 100644 index 0000000000..2d3ee45be8 --- /dev/null +++ b/package/libvncserver/0003-fix-NULL-pointer-dereferences-in-httpd-proxy-handlers.patch @@ -0,0 +1,64 @@ +From dc78dee51a7e270e537a541a17befdf2073f5314 Mon Sep 17 00:00:00 2001 +From: Kazuma Matsumoto <269371721+y637F9QQ2x@users.noreply.github.com> +Date: Thu, 19 Mar 2026 17:42:00 +0900 +Subject: [PATCH] libvncserver: fix NULL pointer dereferences in httpd proxy + handlers + +httpProcessInput() passes the return value of strchr() to atoi() +and strncmp() without checking for NULL. If a CONNECT request +contains no colon, or a GET request contains no slash, strchr() +returns NULL, leading to a segmentation fault. + +Add NULL checks before using the strchr() return values. + +CVE: CVE-2026-32854 +Upstream: https://github.com/LibVNC/libvncserver/commit/dc78dee51a7e270e537a541a17befdf2073f5314 +Signed-off-by: Thomas Perale +--- + src/libvncserver/httpd.c | 24 ++++++++++++++---------- + 1 file changed, 14 insertions(+), 10 deletions(-) + +diff --git a/src/libvncserver/httpd.c b/src/libvncserver/httpd.c +index f4fe51c9..7cefadc4 100644 +--- a/src/libvncserver/httpd.c ++++ b/src/libvncserver/httpd.c +@@ -337,10 +337,11 @@ httpProcessInput(rfbScreenInfoPtr rfbScreen) + + + /* Process the request. */ +- if(rfbScreen->httpEnableProxyConnect) { ++if(rfbScreen->httpEnableProxyConnect) { + const static char* PROXY_OK_STR = "HTTP/1.0 200 OK\r\nContent-Type: octet-stream\r\nPragma: no-cache\r\n\r\n"; + if(!strncmp(buf, "CONNECT ", 8)) { +- if(atoi(strchr(buf, ':')+1)!=rfbScreen->port) { ++ char *colon = strchr(buf, ':'); ++ if(colon == NULL || atoi(colon+1)!=rfbScreen->port) { + rfbErr("httpd: CONNECT format invalid.\n"); + rfbWriteExact(&cl,INVALID_REQUEST_STR, strlen(INVALID_REQUEST_STR)); + httpCloseSock(rfbScreen); +@@ -353,14 +354,17 @@ httpProcessInput(rfbScreenInfoPtr rfbScreen) + rfbScreen->httpSock = RFB_INVALID_SOCKET; + return; + } +- if (!strncmp(buf, "GET ",4) && !strncmp(strchr(buf,'/'),"/proxied.connection HTTP/1.", 27)) { +- /* proxy connection */ +- rfbLog("httpd: client asked for /proxied.connection\n"); +- rfbWriteExact(&cl,PROXY_OK_STR,strlen(PROXY_OK_STR)); +- rfbNewClientConnection(rfbScreen,rfbScreen->httpSock); +- rfbScreen->httpSock = RFB_INVALID_SOCKET; +- return; +- } ++ if (!strncmp(buf, "GET ",4)) { ++ char *slash = strchr(buf, '/'); ++ if (slash != NULL && !strncmp(slash,"/proxied.connection HTTP/1.", 27)) { ++ /* proxy connection */ ++ rfbLog("httpd: client asked for /proxied.connection\n"); ++ rfbWriteExact(&cl,PROXY_OK_STR,strlen(PROXY_OK_STR)); ++ rfbNewClientConnection(rfbScreen,rfbScreen->httpSock); ++ rfbScreen->httpSock = RFB_INVALID_SOCKET; ++ return; ++ } ++ } + } + + if (strncmp(buf, "GET ", 4)) { diff --git a/package/libvncserver/libvncserver.mk b/package/libvncserver/libvncserver.mk index 1180fc8dc7..49c94b8708 100644 --- a/package/libvncserver/libvncserver.mk +++ b/package/libvncserver/libvncserver.mk @@ -13,6 +13,12 @@ LIBVNCSERVER_INSTALL_STAGING = YES LIBVNCSERVER_DEPENDENCIES = host-pkgconf lzo LIBVNCSERVER_CONF_OPTS = -DWITH_LZO=ON +# 0002-add-bounds-checks-to-UltraZip-subrectangle-parsing.patch +LIBVNCSERVER_IGNORE_CVES += CVE-2026-32853 + +# 0003-fix-NULL-pointer-dereferences-in-httpd-proxy-handlers.patch +LIBVNCSERVER_IGNORE_CVES += CVE-2026-32854 + # only used for examples LIBVNCSERVER_CONF_OPTS += \ -DWITH_FFMPEG=OFF \