diff --git a/src/gpu/ganesh/SurfaceContext.cpp b/src/gpu/ganesh/SurfaceContext.cpp
index c6fa47fbca3..02c51c97404 100644
--- a/src/gpu/ganesh/SurfaceContext.cpp
+++ b/src/gpu/ganesh/SurfaceContext.cpp
@@ -58,6 +58,7 @@
 
 #include <algorithm>
 #include <cstdint>
+#include <cstring>
 #include <memory>
 #include <tuple>
 
@@ -1386,6 +1387,20 @@ SurfaceContext::PixelTransferResult SurfaceContext::transferPixels(GrColorType d
     if (!buffer) {
         return {};
     }
+    // GrTransferFromRenderTask::onExecute() can fail silently (its bool return
+    // is discarded by GrDrawingManager) and the entire executeRenderTasks()
+    // pass is skipped if GrResourceAllocator::assign() fails for *any* proxy in
+    // the flush. In both cases the finished-proc still fires and this buffer is
+    // mapped and handed to the client. fBuffersAreInitiallyZero is false on
+    // Vk/GL and clearToZero() refuses kXferGpuToCpu buffers, so map+memset here
+    // to prevent stale GPU-process bytes (e.g. another origin's prior readback
+    // in a shared VMA sub-allocation) from being disclosed when that happens.
+    if (!this->caps()->buffersAreInitiallyZero()) {
+        if (void* p = buffer->map()) {
+            std::memset(p, 0, size);
+            buffer->unmap();
+        }
+    }
     auto srcRect = rect;
     bool flip = this->origin() == kBottomLeft_GrSurfaceOrigin;
     if (flip) {