CVE-2025-49844 PoC — Redis Lua Use-After-Free may lead to remote code execution

Source

https://github.com/dwisiswant0/CVE-2025-49844

Associated Vulnerability

Title: Redis Lua Use-After-Free may lead to remote code execution (CVE-2025-49844)
Description:Redis is an open source, in-memory database that persists on disk. Versions 8.2.1 and below allow an authenticated user to use a specially crafted Lua script to manipulate the garbage collector, trigger a use-after-free and potentially lead to remote code execution. The problem exists in all versions of Redis with Lua scripting. This issue is fixed in version 8.2.2. To workaround this issue without patching the redis-server executable is to prevent users from executing Lua scripts. This can be done using ACL to restrict EVAL and EVALSHA commands.

Description

CVE-2025-49844 – Redis Lua Parser Use-After-Free

Readme

# CVE-2025-49844 – Redis Lua Parser Use-After-Free

Lua chunk-name GC race leading to Redis 8.2.1 use-after-free and remote code execution.

## Overview

Redis embeds Lua 5.1 for scripting. In versions up to 8.2.1 the `luaY_parser` function does NOT anchor the chunk name string on the Lua stack before invoking the lexer. A crafted script can trigger garbage collection while the parser still references the freed string, producing a UAF that leads to native code execution.

## Environment

- Redis server 8.2.1 (or any vulnerable release before 8.2.2)
- `redis-cli`
- Local network access to the Redis instance

## Files

- [`CVE-2025-49844.lua`](/CVE-2025-49844.lua) – hammer the parser with thousands of `loadstring` calls and a GC-enabled chunk name to win the race.

## Usage

```bash
while redis-cli -h localhost -p 6379 --eval CVE-2025-49844.lua >/dev/null; do
    printf '.'
done
```

**Expected result:**

On vulnerable builds the Redis process eventually crashes or drops the connection. Patched 8.2.2 (commit [d5728cb5795c966c5b5b1e0f0ac576a7e69af539](https://github.com/redis/redis/commit/d5728cb5795c966c5b5b1e0f0ac576a7e69af539)) anchors the chunk name and the script runs harmlessly.

## Mitigation

Upgrade to Redis 8.2.2 or later, or disable Lua scripting for untrusted users.

File Snapshot

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