Possible cache poisoning via promiscuous records for the authority section
Summary
| CVE | CVE-2026-42960 |
|---|---|
| State | PUBLISHED |
| Assigner | NLnet Labs |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-20 10:16:28 UTC |
| Updated | 2026-05-20 22:51:43 UTC |
| Description | NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to poisoning via promiscuous records for the authority section. Promiscuous RRSets that complement DNS replies in the authority section can be used to trick Unbound to cache such records. If an adversary is able to attach such records in a reply (i.e., spoofed packet, fragmentation attack) he would be able to poison Unbound's cache. A malicious actor can exploit the possible poisonous effect by injecting RRSets other than NS that are also accompanied by address records in a reply, for example MX. This could be achieved by trying to spoof a reply packet or fragmentation attacks. Unbound would then accept the relative address records in the additional section and cache them if the authority RRSet has enough trust at this point, i.e., in-zone data for the delegation point. Unbound 1.25.1 contains a patch with a fix that disregards address records from the additional section if they are not explicitly relevant only to authority NS records, mitigating the possible poison effect. This is a complement fix to CVE-2025-11411. |
Risk And Classification
Primary CVSS: v4.0 5.7 MEDIUM from [email protected]
CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
EPSS: 0.000270000 probability, percentile 0.081370000 (date 2026-05-27)
Problem Types: CWE-349 | CWE-349 CWE-349: Acceptance of Extraneous Untrusted Data With Trusted Data
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 5.7 | MEDIUM | CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H/E:P/C... |
| 4.0 | CNA | CVSS | 5.7 | MEDIUM | CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H/E:P/U... |
| 3.1 | [email protected] | Primary | 10 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H |
CVSS v4.0 Breakdown
CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | NLnet Labs | Unbound | affected 1.25.1 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| www.nlnetlabs.nl/downloads/unbound/CVE-2026-42960.txt | [email protected] | www.nlnetlabs.nl | Mitigation, Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: TaoFei Guo (Peking University) (en)
CNA: Yang Luo (Tsinghua University) (en)
CNA: JianJun Chen (Tsinghua University) (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2025-11-28T00:00:00.000Z | Issue reported by TaoFei Guo |
| CNA | 2025-11-28T00:00:00.000Z | NLnet Labs acknowledges the report |
| CNA | 2025-12-22T00:00:00.000Z | NLnet Labs shares a patch |
| CNA | 2026-03-16T00:00:00.000Z | TaoFei Guo verifies patch |
| CNA | 2026-05-20T00:00:00.000Z | Fixes released with version 1.25.1 |
Solutions
CNA: This issue is fixed starting with version 1.25.1