Loading vulnerability…
CVE-2026-4893 is an information disclosure and DNS security-control bypass vulnerability in dnsmasq affecting processing of DNS replies that include EDNS0 Client Subnet (ECS) data as defined by RFC 7871. The flaw is described as broken ECS source validation and is associated with incorrect parsing of the OPT record in the check_source() logic. A remote attacker can send a crafted DNS packet containing client-subnet information that causes dnsmasq to bypass source checks that are intended to validate the origin and acceptability of DNS response data. In resolver deployments, this can result in acceptance of forged or malicious DNS data and facilitate cache poisoning or disclosure-related outcomes.
Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
If you can’t patch tonight, do this now.
Patch, then assume compromise.
2 valid exploits after Mallory filtered fakes, detection scripts, and README-only repos.
This repository is a dnsmasq vulnerability verification toolkit centered on CVE-2026-2291, CVE-2026-5172, CVE-2026-4890, CVE-2026-4891, CVE-2026-4892, and CVE-2026-4893. It is not tied to a common exploit framework. The repository contains four functional scripts plus documentation: (1) dnsmasq_cve_verify.py is the primary end-to-end black-box verifier that runs from a testing laptop, starts a malicious DNS service, sends trigger traffic to the DUT, and uses SSH to inspect dnsmasq state and logs before issuing PASS/FAIL verdicts; (2) malicious_dns_server.py is a standalone UDP DNS server that returns crafted malformed responses for manual reproduction of selected parser bugs, notably CVE-2026-5172 and DNSSEC-related issues; (3) test_dnsmasq_cve_remote.py is a lightweight remote detection script that queries version.bind over UDP/53 and infers vulnerability status from the reported dnsmasq version; and (4) test_dnsmasq_cve_on_device.sh is a shell-based local checker that runs on the target device and uses version/strings heuristics to assess patch status and feature applicability. The main exploit capability is network-based triggering of dnsmasq parsing flaws through malicious DNS responses. The code crafts malformed CNAME/rdlen combinations, DNSSEC/NSEC/RRSIG-related records, and ECS-related inputs to induce crashes, hangs, or logic bypasses in vulnerable dnsmasq builds. The README also describes a DHCPv6 CLID overflow test for CVE-2026-4892, which is a local/adjacent vector requiring DHCPv6 support and dhcp-script configuration. The repository therefore mixes active exploit-style verification with auxiliary detection scripts. Because payloads are hardcoded and purpose-built for QA verification rather than generalized post-exploitation, the maturity is best classified as OPERATIONAL rather than weaponized. Fingerprintable observables include the default DUT IP 192.168.1.1, example attacker IP 10.0.0.211, SSH on TCP/22, DNS on UDP/53, trigger domains such as crash-5172.evil.test and crash-2291.evil.test, the version.bind CHAOS TXT query, and DUT file paths like /etc/dnsmasq.conf, /tmp/resolv.conf.auto, /sbin/dnsmasq, /usr/sbin/dnsmasq, and /var/log/messages*. Overall, the repository’s purpose is QA/security validation of dnsmasq patch status and exploitability in live devices, especially routers or embedded Linux systems using dnsmasq as a DNS forwarder.
This repository is a small, focused proof-of-concept exploit for a dnsmasq ECS validation issue. It contains three files: a Python exploit script (exp.py), a sample dnsmasq configuration (dnsmasq.conf), and a short README with setup steps. The exploit is not part of a larger framework. The main logic is in exp.py. It implements a fake upstream UDP DNS server that binds to 127.0.0.1:5354, which matches the upstream server configured in dnsmasq.conf. The script parses incoming DNS queries, only responds if the source IP is 127.0.0.1 (dnsmasq) and the queried name is trigger.evil.com., then sends back a crafted DNS response containing: (1) an A record resolving the trigger name to 1.2.3.4, and (2) an EDNS0 ECS option (code 8) with a deliberately mismatched subnet value of 127.18.0.0/24. The intended capability is to demonstrate that a vulnerable dnsmasq instance improperly accepts this mismatched ECS response from its upstream server. The script also includes a built-in self-test thread. After startup, it sends a DNS query for trigger.evil.com to the configured dnsmasq listener at xxx.xxx.xxx.x:5353, waits for dnsmasq's reply, parses the answer section, and reports the target as vulnerable if dnsmasq returns the fake IP 1.2.3.4. This makes the repository both an exploit PoC and a validation harness. Repository structure and purpose: - exp.py: primary exploit and verification logic; contains DNS packet parsing, DNS response crafting, ECS option construction, UDP listener, and self-test. - dnsmasq.conf: minimal sample configuration showing dnsmasq listening on port 5353 and forwarding to 127.0.0.1:5354. - readme.txt: setup instructions, including enabling add-subnet and running the Python script. Overall, this is an operational network-based PoC for testing whether dnsmasq accepts attacker-controlled upstream DNS replies with mismatched ECS metadata. It does not deliver code execution; instead, it demonstrates DNS response spoofing/poisoning-style behavior by causing dnsmasq to return an attacker-chosen IP for a controlled domain under specific configuration conditions.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
14 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An upstream dnsmasq vulnerability fixed via backport in OpenWrt's dnsmasq package.
An information disclosure flaw in dnsmasq that allows remote attackers to bypass source checks using a crafted DNS packet containing RFC 7871 client-subnet information.
An information disclosure and source-check bypass vulnerability in dnsmasq triggered by crafted DNS packets containing RFC 7871 client-subnet information.
A Dnsmasq DNS response validation flaw involving EDNS0 client subnet handling in check_source(), which can allow spoofed DNS responses to be accepted.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.