diff --git a/ChangeLog.d/fix-tricore-muladdc-clobber.txt b/ChangeLog.d/fix-tricore-muladdc-clobber.txt
new file mode 100644
index 0000000000..66ff793d2b
--- /dev/null
+++ b/ChangeLog.d/fix-tricore-muladdc-clobber.txt
@@ -0,0 +1,8 @@
+Bugfix
+   * Fix the TriCore MULADDC inline assembly in library/bn_mul.h which was
+     missing register d5 (the high half of the e4 carry-in pair) from its
+     clobber list. On TriCore 1.8 (AURIX TC4xx) the compiler could allocate
+     a live value in d5 across the asm block, which the asm then overwrote,
+     corrupting the carry chain. This produced wrong results in
+     mbedtls_mpi_core_mla, making mbedtls_mpi_mod_mpi loop forever. Declare
+     all data registers the asm writes so the compiler does not reuse them.
diff --git a/library/bn_mul.h b/library/bn_mul.h
index 0738469db4..84053a1c46 100644
--- a/library/bn_mul.h
+++ b/library/bn_mul.h
@@ -653,7 +653,8 @@
         "st.a   %2, %%a2                \n\t"   \
         : "=m" (c), "=m" (d), "=m" (s)          \
         : "m" (s), "m" (d), "m" (c), "m" (b)    \
-        : "d0", "d1", "e2", "d4", "a2", "a3"    \
+        : "d0", "d1", "d2", "d3", "d4", "d5",   \
+          "a2", "a3"                            \
     );
 
 #endif /* TriCore */