# CVE-2026-33630: Use after free in c-ares

> A use-after-free in c-ares allows remote attackers to execute code or cause denial of service via TCP queries.

- **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:** 3 Sep 2026
- **Updated:** 5 Sep 2026
- **Also known as:** ALPINE-CVE-2026-33630, ALSA-2026:42096, AZL-99093, AZL-99095, BELL-CVE-2026-33630, DEBIAN-CVE-2026-33630, ECHO-3b80-9e26-3298, GHSA-6wfj-rwm7-3542, MINI-v7pm-5956-rc34, RHSA-2026:36192, RHSA-2026:42096, RLSA-2026:42096, ROOT-OS-ALPINE-320-CVE-2026-33630, UBUNTU-CVE-2026-33630, USN-8844-1

## What is CVE-2026-33630?

CVE-2026-33630 is a high-severity use after free vulnerability in c-ares, published on 3 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

c-ares is an asynchronous resolver library. From ver 1.32.3 until 1.34.7, a use-after-free / double-free in c-ares' query-completion handling. The same flaw — a query's callback being invoked while the query is still linked in the channel's internal lookup structures — is present at multiple points in the resend/finish path (timeout handling, response handling, and query dispatch). If the query, or for ares_getaddrinfo() the owning host_query, is freed as a side effect of that callback, it is then accessed and/or freed a second time. This vulnerability is fixed in ver 1.34.7.

Weakness: CWE-416 (Use After Free), CWE-415 (Double Free)

## Which versions are affected by CVE-2026-33630?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `c-ares` | AlmaLinux:10 | All versions | 1.34.6-2.el10_2 |
| `c-ares-devel` | AlmaLinux:10 | All versions | 1.34.6-2.el10_2 |
| `c-ares` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.34.6-2.el10_2 |
| `c-ares-debuginfo` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.34.6-2.el10_2 |
| `c-ares-debugsource` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.34.6-2.el10_2 |
| `c-ares-devel` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.34.6-2.el10_2 |
| `c-ares` | Red Hat:hummingbird:1 | All versions | 0:1.34.7-1.hum1 |
| `c-ares-devel` | Red Hat:hummingbird:1 | All versions | 0:1.34.7-1.hum1 |
| `c-ares` | Rocky Linux:10 | All versions | 0:1.34.6-2.el10_2 |

## How do I fix CVE-2026-33630?

Upgrade to a fixed version.

## Is CVE-2026-33630 being exploited?

There is no known exploitation of CVE-2026-33630 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33630 and fix it if it is affected.

What it is: CVE-2026-33630 is a high-severity use after free vulnerability in c-ares, published on 3 Sep 2026. 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-2026-33630 in the wild and no public exploit code.

Affected product: c-ares. 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-2026-33630/ (Markdown: https://insights.sbomify.com/CVE-2026-33630/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33630
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33630
- OSV: https://osv.dev/vulnerability/CVE-2026-33630

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33630/
Summaries are generated and may contain mistakes; the official description above is the record.