Vulnerability in Twisted (CVE-2026-42304)
Summary
Vulnerability in Twisted (CVE-2026-42304). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 26.4.0rc2 or later.
Original description
The description as published by the source.
Details
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.
Technical Details
The main issue is in twisted.names.dns.Name.decode. A visited set was added in 2011 (commit e11cd82) to prevent infinite loops, but there is still no limit on the number of pointer dereferences per message. Also, the visited set is reset for each Question record.
Because DNSServerFactory handles every record in QDCOUNT without checking them, an attacker can add thousands of questions that all refer to the same long chain of pointers. This makes the parser repeat a complex and unnecessary search.
## src/twisted/names/dns.py (Lines 595-631)
def decode(self, strio, length=None):
visited = set()
self.name = b""
off = 0
while 1:
l = ord(readPrecisely(strio, 1))
if l == 0:
if off > 0:
strio.seek(off)
return
if (l >> 6) == 3:
new_off = (l & 63) << 8 | ord(readPrecisely(strio, 1))
if new_off in visited:
raise ValueErro…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-42304 has been found in Twisted.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade Twisted to 26.4.0rc2 or later.
If unsure, ask your IT team or search "Twisted CVE-2026-42304" on the vendor's site.
CVE-2026-42304 (Twisted) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 26.4.0rc2 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-400) exists in Twisted.
Check the vendor advisory for the affected versions of Twisted.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 26.4.0rc2.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Twisted' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'Twisted' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
Twistedを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade Twisted to 26.4.0rc2ステージング環境で 26.4.0rc2 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2026-42304 py3-twisted Fixed in: 22.10.0-r2
- Debian DEBIAN-CVE-2026-42304 twisted
- Ubuntu UBUNTU-CVE-2026-42304 twisted
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com