Submit #850385: radareorg radare2 6.1.6 Integer Overflow

> This report was generated by AI and manually verified by a human.

## Environment

```sh
# copypaste this script into your shell and replace it with the output
date
r2 -v
uname -ms
```

## Description

`r_str_append` in `libr/util/str.c` can overflow signed `int` arithmetic while computing the required appended string size.

A harness linked against the sanitized `libr_util` drives the size calculation to `2147483647 + 1`. UBSan reports signed integer overflow at `libr/util/str.c:870:36`.

The expected behavior is to use checked size arithmetic and reject append operations whose computed size exceeds the supported range.

## Test

PoC:

- [r_str_append_overflow_harness.c](https://github.com/Bin-infinite/vuln-validations/blob/main/radare2/target/case-027/pocs/r_str_append_overflow_harness.c)
- [run_r_str_append_overflow.sh](https://github.com/Bin-infinite/vuln-validations/blob/main/radare2/target/case-027/pocs/run_r_str_append_overflow.sh)

Reproducer:

```sh
ROOT="$PWD"
curl -LO https://raw.githubusercontent.com/Bin-infinite/vuln-validations/main/radare2/target/case-027/pocs/r_str_append_overflow_harness.c

clang -fsanitize=address,undefined -fno-omit-frame-pointer -g -O0 \
-I"$ROOT/libr/include" \
-I"$ROOT/build" \
-I"$ROOT/shlr/sdb/include" \
-L"$ROOT/build/libr/util" \
-Wl,-rpath,"$ROOT/build/libr/util" \
-o /tmp/r_str_append_overflow_harness \
r_str_append_overflow_harness.c \
-lr_util

ASAN_OPTIONS=detect_leaks=0 \
UBSAN_OPTIONS=halt_on_error=0:print_stacktrace=1 \
/tmp/r_str_append_overflow_harness
```

Expected sanitizer result:

```text
libr/util/str.c:870:36: runtime error: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
```

Stack trace excerpt:

```text
#0 r_str_append libr/util/str.c:870
#1 main row-validation-output/case-027/pocs/r_str_append_overflow_harness.c:108
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior libr/util/str.c:870:36
```

• Source: ⚠️ https://github.com/radareorg/radare2/issues/26045
• User: Kery Qi (UID 94424)
• Submission: 06/06/2026 07:31 (29 days ago)
• Moderation: 07/04/2026 18:19 (28 days later)
• Status: Accepted
• VulDB entry: 376350 [radareorg radare2 up to 6.1.6 libr/util/str.c r_str_ndup/r_str_append integer overflow]
• Points: 20