# CVE-2021-32675: DoS vulnerability in Redis

> Unauthenticated attackers can cause memory exhaustion and denial of service in Redis by sending specially crafted RESP requests.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Oct 2021
- **Updated:** 3 Aug 2024
- **Also known as:** ALPINE-CVE-2021-32675, AZL-6848, BIT-keydb-2021-32675, BIT-redis-2021-32675, BIT-valkey-2021-32675, CLEANSTART-2026-PG73171, DEBIAN-CVE-2021-32675, GHSA-f6pw-v9gw-v64p, UBUNTU-CVE-2021-32675

## What is CVE-2021-32675?

CVE-2021-32675 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 4 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Redis is an open source, in-memory database that persists on disk. When parsing an incoming Redis Standard Protocol (RESP) request, Redis allocates memory according to user-specified values which determine the number of elements (in the multi-bulk header) and size of each element (in the bulk header). An attacker delivering specially crafted requests over multiple connections can cause the server to allocate significant amount of memory. Because the same parsing mechanism is used to handle authentication requests, this vulnerability can also be exploited by unauthenticated users. The problem is fixed in Redis versions 6.2.6, 6.0.16 and 5.0.14. An additional workaround to mitigate this problem without patching the redis-server executable is to block access to prevent unauthenticated users from connecting to Redis. This can be done in different ways: Using network access control tools like firewalls, iptables, security groups, etc. or Enabling TLS and requiring users to authenticate using client side certificates.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2021-32675?

3 open source packages ship an affected version, including keydb, redis and valkey. It affects 6 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `keydb` | Bitnami | From 5.0.0 | 5.0.14, 6.0.16, 6.2.6 |
| `redis` | Bitnami | From 5.0.0 | 5.0.14, 6.0.16, 6.2.6 |
| `valkey` | Bitnami | From 5.0.0 | 5.0.14, 6.0.16, 6.2.6 |

Products: Debian Debian Linux, Fedoraproject Fedora, Netapp Management Services for Element Software, Netapp Management Services for Netapp Hci, Oracle Communications Operations Monitor, Redis Redis.

## How do I fix CVE-2021-32675?

Upgrade keydb to a fixed version for your release line: 5.0.14, 6.0.16 or 6.2.6.

## Is CVE-2021-32675 being exploited?

There is no known exploitation of CVE-2021-32675 in the wild and no public exploit code.

Public exploit code:

- https://github.com/rubbxalc/CVE-2021-32675 (github_poc): https://github.com/rubbxalc/CVE-2021-32675

## 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-2021-32675 and fix it if it is affected.

What it is: CVE-2021-32675 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 4 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-32675 in the wild and no public exploit code.

Affected packages and fixed versions:
- keydb (Bitnami): affected from 5.0.0; fixed in 5.0.14, 6.0.16, 6.2.6
- redis (Bitnami): affected from 5.0.0; fixed in 5.0.14, 6.0.16, 6.2.6
- valkey (Bitnami): affected from 5.0.0; fixed in 5.0.14, 6.0.16, 6.2.6

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-2021-32675/ (Markdown: https://insights.sbomify.com/CVE-2021-32675/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-32675
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-32675
- OSV: https://osv.dev/vulnerability/CVE-2021-32675

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-32675/
Summaries are generated and may contain mistakes; the official description above is the record.