CVE-2021-32765
Publication date 4 October 2021
Last updated 26 August 2025
Ubuntu priority
Description
Hiredis is a minimalistic C client library for the Redis database. In affected versions Hiredis is vulnurable to integer overflow if provided maliciously crafted or corrupted `RESP` `mult-bulk` protocol data. When parsing `multi-bulk` (array-like) replies, hiredis fails to check if `count * sizeof(redisReply*)` can be represented in `SIZE_MAX`. If it can not, and the `calloc()` call doesn't itself make this check, it would result in a short allocation and subsequent buffer overflow. Users of hiredis who are unable to update may set the [maxelements](https://github.com/redis/hiredis#reader-max-array-elements) context option to a value small enough that no overflow is possible.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| hiredis | 25.10 questing |
Not affected
|
| 25.04 plucky |
Not affected
|
|
| 24.04 LTS noble |
Not affected
|
|
| 22.04 LTS jammy |
Not affected
|
|
| 20.04 LTS focal |
Not affected
|
|
| 18.04 LTS bionic |
Not affected
|
|
| 16.04 LTS xenial |
Vulnerable
|
|
| 14.04 LTS trusty |
Not affected
|
Notes
seth-arnold
This feels like a bug in calloc() implementation, not in Hiredis. I'm marking this not-affected for us because our calloc(3) should do the right thing.
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
8.8 · High
|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | Low |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity impact | High |
| Availability impact | High |
| Vector | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |