diff --git a/include/supportbase.h b/include/supportbase.h
index 95a57ae023..26929e054e 100644
--- a/include/supportbase.h
+++ b/include/supportbase.h
@@ -52,6 +52,7 @@ void sbCreateFolders(const char *path, int createDiscImgFolders);
 
 // ISO9660 filesystem management functions.
 u32 sbGetISO9660MaxLBA(const char *path);
+u32 sbGetMediaLsnCount(const char *path, u64 totalBytes);
 int sbProbeISO9660(const char *path, base_game_info_t *game, u32 layer1_offset);
 int sbProbeISO9660_64(const char *path, base_game_info_t *game, u32 layer1_offset);
 
diff --git a/modules/iopcore/cdvdman/searchfile.c b/modules/iopcore/cdvdman/searchfile.c
index e409e82afb..e03ce9f449 100644
--- a/modules/iopcore/cdvdman/searchfile.c
+++ b/modules/iopcore/cdvdman/searchfile.c
@@ -263,4 +263,13 @@ void cdvdman_searchfile_init(void)
             DPRINTF("cdvdman_searchfile_init DVD9 mediaLsnCount=%d\n", mediaLsnCount);
         }
     }
+
+    // The PVD Volume Space Size only describes the ISO9660 volume, not the whole disc.
+    // Badly mastered discs (e.g. SLES_533.98) keep data past the end of the volume and
+    // read it by raw LBA, which works on real hardware. Prefer the real media sector
+    // count measured by the loader whenever it was provided.
+    if (cdvdman_settings.common.mediaLsnCount) {
+        mediaLsnCount = cdvdman_settings.common.mediaLsnCount;
+        DPRINTF("cdvdman_searchfile_init loader-provided mediaLsnCount=%d\n", mediaLsnCount);
+    }
 }
diff --git a/modules/iopcore/common/cdvd_config.h b/modules/iopcore/common/cdvd_config.h
index 237d7b2783..5e9ef3f506 100644
--- a/modules/iopcore/common/cdvd_config.h
+++ b/modules/iopcore/common/cdvd_config.h
@@ -33,6 +33,7 @@ struct cdvdman_settings_common
     u8 zso_cache;
     u8 fakemodule_flags;
     u8 padding;
+    u32 mediaLsnCount; // Real sector count of the media. 0 = fall back to the ISO9660 PVD Volume Space Size.
 } __attribute__((packed));
 
 struct cdvdman_settings_hdd
@@ -88,9 +89,9 @@ struct cdvdman_settings_bdm
     bd_fragment_t frags[BDM_MAX_FRAGS];
 } __attribute__((packed));
 
-#define CDVDMAN_SETTINGS_DEFAULT_COMMON                    \
-    {                                                      \
-        0x68, 0x68, 0x1234, 0x39393939, "DSKID", 16, 8, 16 \
+#define CDVDMAN_SETTINGS_DEFAULT_COMMON                                \
+    {                                                                  \
+        0x68, 0x68, 0x1234, 0x39393939, "DSKID", 16, 8, 16, 0x87654321 \
     }
 #define CDVDMAN_SETTINGS_DEFAULT_HDD 0x12345678
 #define CDVDMAN_SETTINGS_DEFAULT_SMB                          \
diff --git a/src/bdmsupport.c b/src/bdmsupport.c
index b181dec6a0..fac694d032 100644
--- a/src/bdmsupport.c
+++ b/src/bdmsupport.c
@@ -318,6 +318,7 @@ void bdmLaunchGame(item_list_t *itemList, int id, config_set_t *configSet)
     int i, fd, iop_fd, index, compatmask = 0;
     int EnablePS2Logo = 0;
     int result;
+    u64 isoTotalBytes = 0;
     u64 startingLBA;
     unsigned int startCluster;
     char partname[256], filename[32];
@@ -459,6 +460,8 @@ void bdmLaunchGame(item_list_t *itemList, int id, config_set_t *configSet)
         iso_frag->frag_count += iFragCount;
         iTotalFragCount += iFragCount;
 
+        isoTotalBytes += lseek64(fd, 0, SEEK_END);
+
         if ((gPS2Logo) && (i == 0))
             EnablePS2Logo = CheckPS2Logo(fd, 0);
 
@@ -469,6 +472,11 @@ void bdmLaunchGame(item_list_t *itemList, int id, config_set_t *configSet)
     sbCreatePath(game, partname, pDeviceData->bdmPrefix, "/", 0);
     layer1_start = sbGetISO9660MaxLBA(partname);
 
+    // Real media size, for CDVDMAN's out-of-bounds read emulation. The ISO9660 PVD
+    // cannot be trusted for this: badly mastered discs understate it and read data
+    // past the end of the volume by raw LBA.
+    settings->common.mediaLsnCount = sbGetMediaLsnCount(partname, isoTotalBytes);
+
     switch (game->format) {
         case GAME_FORMAT_USBLD:
             layer1_part = layer1_start / 0x80000;
diff --git a/src/ethsupport.c b/src/ethsupport.c
index f0462fa42a..3fbd3f8904 100644
--- a/src/ethsupport.c
+++ b/src/ethsupport.c
@@ -15,6 +15,7 @@
 
 #define NEWLIB_PORT_AWARE
 #include <fileXio_rpc.h> // fileXioDevctl(ethBase, SMB_***)
+#include <ps2sdkapi.h>   // lseek64
 
 #include "include/nbns.h"
 #include "httpclient.h"
@@ -668,6 +669,18 @@ static void ethLaunchGame(item_list_t *itemList, int id, config_set_t *configSet
     strcpy(settings->smb_user, gPCUserName);
     strcpy(settings->smb_password, gPCPassword);
 
+    // Sum the size of all parts, for CDVDMAN's out-of-bounds read emulation.
+    u64 isoTotalBytes = 0;
+    int part;
+    for (part = 0; part < game->parts; part++) {
+        sbCreatePath(game, partname, ethPrefix, "\\", part);
+        int fd = open(partname, O_RDONLY, 0666);
+        if (fd >= 0) {
+            isoTotalBytes += lseek64(fd, 0, SEEK_END);
+            close(fd);
+        }
+    }
+
     // Initialize layer 1 information.
     sbCreatePath(game, partname, ethPrefix, "\\", 0);
 
@@ -681,6 +694,10 @@ static void ethLaunchGame(item_list_t *itemList, int id, config_set_t *configSet
 
     layer1_start = sbGetISO9660MaxLBA(partname);
 
+    // Real media size; the ISO9660 PVD cannot be trusted for this (badly mastered
+    // discs understate it and read data past the end of the volume by raw LBA).
+    settings->common.mediaLsnCount = sbGetMediaLsnCount(partname, isoTotalBytes);
+
     switch (game->format) {
         case GAME_FORMAT_USBLD:
             layer1_part = layer1_start / 0x80000;
diff --git a/src/hddsupport.c b/src/hddsupport.c
index 1f3eaefa87..5aa330e019 100644
--- a/src/hddsupport.c
+++ b/src/hddsupport.c
@@ -578,6 +578,11 @@ void hddLaunchGame(item_list_t *itemList, int id, config_set_t *configSet)
     // patch start_sector
     settings->lba_start = game->start_sector;
 
+    // Real media size, for CDVDMAN's out-of-bounds read emulation. The ISO9660 PVD
+    // cannot be trusted for this: badly mastered discs understate it and read data
+    // past the end of the volume by raw LBA.
+    settings->common.mediaLsnCount = game->total_size_in_kb / 2;
+
     if (configGetStrCopy(configSet, CONFIG_ITEM_ALTSTARTUP, filename, sizeof(filename)) == 0)
         strcpy(filename, game->startup);
 
@@ -596,6 +601,8 @@ void hddLaunchGame(item_list_t *itemList, int id, config_set_t *configSet)
         if (maxLBA > 0 && maxLBA < ziso_total_block) {   // dual layer check
             settings->common.layer1_start = maxLBA - 16; // adjust second layer start
         }
+        // For compressed images the partition size does not match the media size.
+        settings->common.mediaLsnCount = ziso_total_block;
     }
 
     if (gAutoLaunchGame == NULL)
diff --git a/src/supportbase.c b/src/supportbase.c
index 63cd6ad2e4..0a1f988efa 100644
--- a/src/supportbase.c
+++ b/src/supportbase.c
@@ -518,6 +518,26 @@ u32 sbGetISO9660MaxLBA(const char *path)
     return maxLBA;
 }
 
+u32 sbGetMediaLsnCount(const char *path, u64 totalBytes)
+{
+    u32 lsnCount;
+    int fd;
+
+    // For compressed images the file size does not match the media size, so use
+    // the uncompressed sector count from the ZISO header instead.
+    lsnCount = 0;
+    if ((fd = open(path, O_RDONLY, 0666)) >= 0) {
+        if (ProbeZISO(fd))
+            lsnCount = ziso_total_block;
+        close(fd);
+    }
+
+    if (lsnCount == 0)
+        lsnCount = (u32)(totalBytes / 2048);
+
+    return lsnCount;
+}
+
 int sbProbeISO9660(const char *path, base_game_info_t *game, u32 layer1_offset)
 {
     int result = -1, fd;
@@ -576,6 +596,7 @@ int sbPrepare(base_game_info_t *game, config_set_t *configSet, int size_cdvdman,
         settings->media = game->media;
     }
     settings->flags = 0;
+    settings->mediaLsnCount = 0;
 
     if (compatmask & COMPAT_MODE_1) {
         settings->flags |= IOPCORE_COMPAT_ACCU_READS;