CVE-2026-42304 Twisted: Denial of Service (DoS) in twisted.names via Crafted DNS Compression Pointer Chains
Remote attackers can cause denial of service in Twisted applications by sending crafted DNS packets that trigger resource exhaustion during name decompression.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42304?
CVE-2026-42304 is a high-severity denial of service vulnerability in twisted, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.4.0rc2, the twisted.names module is vulnerable to a Denial of Service (DoS) attack via resource exhaustion during DNS name decompression. A remote, unauthenticated attacker can exploit this by sending a crafted TCP DNS packet containing deeply chained compression pointers. This flaw bypasses previous loop-prevention logic, causing the single-threaded Twisted reactor to hang while processing millions of recursive lookups, effectively freezing the server. This vulnerability is fixed in 26.4.0rc2.
Which versions are affected by CVE-2026-42304?
3 open source packages ship an affected version, including twisted and Twisted. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
twisted PyPI | All versions | 26.4.0 |
twisted PyPI | All versions | 26.4.0rc2 |
Twisted PyPI | All versions | 26.4.0rc2 |
Linux distribution packages (3)
python-Twisted SUSE:Linux Enterprise Server 16.0 | All versions | 24.10.0-160000.3.1 |
python-Twisted SUSE:Linux Enterprise Server for SAP applications 16.0 | All versions | 24.10.0-160000.3.1 |
python-Twisted openSUSE:Tumbleweed | All versions | 26.4.0-1.1 |
Products include Twisted Twisted.
How do I fix CVE-2026-42304?
Upgrade twisted to a fixed version for your release line: 26.4.0 or 26.4.0rc2.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-42304 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42304 exists.
Other vulnerabilities in twisted
Sources
Also known as AZL-86751, BELL-CVE-2026-42304, CLEANSTART-2026-FF58262, CLEANSTART-2026-XG33120, DEBIAN-CVE-2026-42304, GHSA-grgv-6hw6-v9g4 and 13 more.