# CVE-2021-32765: Integer Overflow to Buffer Overflow in Hiredis

> An integer overflow in Hiredis when parsing multi-bulk replies can lead to buffer overflow, allowing attackers to execute code or cause denial of service.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Oct 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-32765, GHSA-hfm9-39pp-55p2, MGASA-2021-0562, OESA-2021-1390, UBUNTU-CVE-2021-32765, openSUSE-SU-2021:1536-1, openSUSE-SU-2021:1550-1, openSUSE-SU-2024:11561-1

## What is CVE-2021-32765?

CVE-2021-32765 is a high-severity vulnerability in Debian Debian Linux, published on 4 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-680 (Integer Overflow to Buffer Overflow), CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2021-32765?

It affects 3 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hiredis` | SUSE:Package Hub 15 SP2 | All versions | 0.13.3-bp152.4.3.1 |
| `hiredis` | SUSE:Package Hub 15 SP3 | All versions | 0.13.3-bp153.2.3.1 |
| `hiredis` | openSUSE:Leap 15.2 | All versions | 0.13.3-bp153.2.3.1 |
| `hiredis` | openSUSE:Leap 15.3 | All versions | 0.13.3-bp153.2.3.1 |
| `hiredis` | openSUSE:Tumbleweed | All versions | 1.0.2-1.1 |

Products: Debian Debian Linux, Netapp Management Services for Element Software and Netapp Hci, Redis Hiredis.

## How do I fix CVE-2021-32765?

Upgrade to a fixed version.

## Is CVE-2021-32765 being exploited?

There is no known exploitation of CVE-2021-32765 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-32765 and fix it if it is affected.

What it is: CVE-2021-32765 is a high-severity vulnerability in Debian Debian Linux, published on 4 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-32765 in the wild and no public exploit code.

Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-32765/ (Markdown: https://insights.sbomify.com/CVE-2021-32765/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-32765
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-32765
- OSV: https://osv.dev/vulnerability/CVE-2021-32765

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-32765/
Summaries are generated and may contain mistakes; the official description above is the record.