https://vulnerability.circl.lu Contains only the most 10 recent entries. http://www.rssboard.org/rss-specification python-feedgen en Thu, 01 Oct 2026 01:54:59 +0000 https://vulnerability.circl.lu/vuln/ghsa-grgv-6hw6-v9g4 <p><strong>Affected:</strong> PyPI: Twisted</p> <p>### Details</p> <p>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.</p> <p>---</p> <p>### Technical Details</p> <p>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.</p> <p>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.</p> <p>```python ## src/twisted/names/dns.py (Lines 595-631)</p> <p>def decode(self, strio, length=None): visited = set() self.name = b&#34;&#34; off = 0 while 1: l = ord(readPrecisely(strio, 1)) if l == 0: if off &gt; 0: strio.seek(off) return if (l &gt;&gt; 6) == 3: new_off = (l &amp; 63) &lt;&lt; 8 | ord(readPrecisely(strio, 1)) if new_off in visited: raise ValueErr…</p> <p><strong>Affected:</strong> PyPI: Twisted</p> <p>### Details</p> <p>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.</p> <p>---</p> <p>### Technical Details</p> <p>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.</p> <p>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.</p> <p>```python ## src/twisted/names/dns.py (Lines 595-631)</p> <p>def decode(self, strio, length=None): visited = set() self.name = b&#34;&#34; off = 0 while 1: l = ord(readPrecisely(strio, 1)) if l == 0: if off &gt; 0: strio.seek(off) return if (l &gt;&gt; 6) == 3: new_off = (l &amp; 63) &lt;&lt; 8 | ord(readPrecisely(strio, 1)) if new_off in visited: raise ValueErr…</p> https://vulnerability.circl.lu/vuln/ghsa-grgv-6hw6-v9g4