diff --git a/base/strings/util.jl b/base/strings/util.jl
index d624c612cd29c..b97a76a24b3e8 100644
--- a/base/strings/util.jl
+++ b/base/strings/util.jl
@@ -243,7 +243,7 @@ function lpad(
     n::Integer,
     p::Union{AbstractChar,AbstractString}=' ',
 ) :: String
-    m = n - length(s)
+    m = signed(n) - length(s)
     m ≤ 0 && return string(s)
     l = length(p)
     q, r = divrem(m, l)
@@ -270,7 +270,7 @@ function rpad(
     n::Integer,
     p::Union{AbstractChar,AbstractString}=' ',
 ) :: String
-    m = n - length(s)
+    m = signed(n) - length(s)
     m ≤ 0 && return string(s)
     l = length(p)
     q, r = divrem(m, l)
diff --git a/src/array.c b/src/array.c
index 1afceb7054a56..5256ccf7266d0 100644
--- a/src/array.c
+++ b/src/array.c
@@ -471,6 +471,8 @@ JL_DLLEXPORT jl_value_t *jl_array_to_string(jl_array_t *a)
 JL_DLLEXPORT jl_value_t *jl_pchar_to_string(const char *str, size_t len)
 {
     size_t sz = sizeof(size_t) + len + 1; // add space for trailing \nul protector and size
+    if (sz < len) // overflow
+        jl_throw(jl_memory_exception);
     if (len == 0)
         return jl_an_empty_string;
     jl_value_t *s = jl_gc_alloc_(jl_get_ptls_states(), sz, jl_string_type); // force inlining
@@ -483,6 +485,8 @@ JL_DLLEXPORT jl_value_t *jl_pchar_to_string(const char *str, size_t len)
 JL_DLLEXPORT jl_value_t *jl_alloc_string(size_t len)
 {
     size_t sz = sizeof(size_t) + len + 1; // add space for trailing \nul protector and size
+    if (sz < len) // overflow
+        jl_throw(jl_memory_exception);
     if (len == 0)
         return jl_an_empty_string;
     jl_value_t *s = jl_gc_alloc_(jl_get_ptls_states(), sz, jl_string_type); // force inlining
diff --git a/test/strings/basic.jl b/test/strings/basic.jl
index af17c4dee095a..25ee4c9ea8ea0 100644
--- a/test/strings/basic.jl
+++ b/test/strings/basic.jl
@@ -606,6 +606,8 @@ end
         @test repeat(s, 3) === S
         @test repeat(S, 3) === S*S*S
     end
+    # Issue #32160 (string allocation unsigned overflow)
+    @test_throws OutOfMemoryError repeat('x', typemax(Csize_t))
 end
 @testset "issue #12495: check that logical indexing attempt raises ArgumentError" begin
     @test_throws ArgumentError "abc"[[true, false, true]]
diff --git a/test/strings/util.jl b/test/strings/util.jl
index 43d88853c4db9..59024e972021b 100644
--- a/test/strings/util.jl
+++ b/test/strings/util.jl
@@ -41,6 +41,9 @@
     @test rpad("αβ", 8, "¹₂³") == "αβ¹₂³¹₂³"
     @test lpad("αβ", 9, "¹₂³") == "¹₂³¹₂³¹αβ"
     @test rpad("αβ", 9, "¹₂³") == "αβ¹₂³¹₂³¹"
+    # Issue #32160 (unsigned underflow in lpad/rpad)
+    @test lpad("xx", UInt(1), " ") == "xx"
+    @test rpad("xx", UInt(1), " ") == "xx"
 end
 
 # string manipulation