Cross-zone wildcard cache poisoning via RRSIG.labels manipulation
In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, insufficient validation of the RRSIG.Labels field combined with premature cache writes during RFC 8198 aggressive NSEC processing leads to cache poisoning that permits a malicious actor controlling a single delegated zone to poison arbitrary sibling zones under NSEC-signed parent domains. A malicious actor with one registered domain under an NSEC-signed TLD can serve malicious insecure DNS responses for unrelated sibling domains (sharing the same parent zone). Arbitrary delegations that do not exist under the parent domain and are covered by the parent's NSEC chain can be brought into insecure existence by fraudulent wildcard DS records (less labels than expected, unknown algorithm) from the malicious sibling domain. This allows the malicious actor to inject insecure wildcard records for those delegations.
- ALSA-2026:55784
- ALSA-2026:55841
- ALSA-2026:55892
- openSUSE-SU-2026:11380-1
- openSUSE-SU-2026:21550-1
- RHSA-2026:43588
- RHSA-2026:55784
- RHSA-2026:55841
- RHSA-2026:55892
- RLSA-2026:55784
- RLSA-2026:55841
- RLSA-2026:55892
- SUSE-SU-2026:23050-1
- SUSE-SU-2026:23215-1
- SUSE-SU-2026:23226-1
- SUSE-SU-2026:23349-1
- SUSE-SU-2026:23360-1
- SUSE-SU-2026:3884-1
- SUSE-SU-2026:3885-1
- Published
- Jul 22, 2026
- Updated
- Jul 24, 2026
- EPSS
- 0.1% · 3th percentile
- CWE
- CWE-345
Sign in to follow · You’ll be notified if a followed record enters KEV, gets an exploit or is updated.
Report tools
Action score
30
Monitor
Low priority for now.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.1%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · NLnet Labs
- 7.5
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
| Vendor | Product | CPE |
|---|---|---|
| nlnetlabs | unbound | cpe:2.3:a:nlnetlabs:unbound |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- nlnetlabs unbound1.7.0 and later · before 1.25.2
Versions reported by the vendor
Affected version ranges reported by the assigning authority (NLnet Labs). Independent of NVD's CPE analysis and usually ahead of it.
NLnet Labs Unbound
- 1.7.0 and later · before 1.25.2affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:10 | python3-unbound | before 1.24.2-7.el10_2.4 | 1.24.2-7.el10_2.4 |
| AlmaLinux:10 | unbound | before 1.24.2-7.el10_2.4 | 1.24.2-7.el10_2.4 |
| AlmaLinux:10 | unbound-anchor | before 1.24.2-7.el10_2.4 | 1.24.2-7.el10_2.4 |
| AlmaLinux:10 | unbound-devel | before 1.24.2-7.el10_2.4 | 1.24.2-7.el10_2.4 |
| AlmaLinux:10 | unbound-dracut | before 1.24.2-7.el10_2.4 | 1.24.2-7.el10_2.4 |
| AlmaLinux:10 | unbound-libs | before 1.24.2-7.el10_2.4 | 1.24.2-7.el10_2.4 |
| AlmaLinux:10 | unbound-utils | before 1.24.2-7.el10_2.4 | 1.24.2-7.el10_2.4 |
| AlmaLinux:8 | python3-unbound | before 1.16.2-5.14.el8_10 | 1.16.2-5.14.el8_10 |
| AlmaLinux:8 | unbound | before 1.16.2-5.14.el8_10 | 1.16.2-5.14.el8_10 |
| AlmaLinux:8 | unbound-devel | before 1.16.2-5.14.el8_10 | 1.16.2-5.14.el8_10 |
| AlmaLinux:8 | unbound-libs | before 1.16.2-5.14.el8_10 | 1.16.2-5.14.el8_10 |
| AlmaLinux:9 | python3-unbound | before 1.24.2-3.el9_8.4 | 1.24.2-3.el9_8.4 |
| AlmaLinux:9 | unbound | before 1.24.2-3.el9_8.4 | 1.24.2-3.el9_8.4 |
| AlmaLinux:9 | unbound-devel | before 1.24.2-3.el9_8.4 | 1.24.2-3.el9_8.4 |
| AlmaLinux:9 | unbound-dracut | before 1.24.2-3.el9_8.4 | 1.24.2-3.el9_8.4 |
| AlmaLinux:9 | unbound-libs | before 1.24.2-3.el9_8.4 | 1.24.2-3.el9_8.4 |
| Alpine:v3.22 | unbound | from 1.7.0 · before 1.25.2-r0 | 1.25.2-r0 |
| Debian:12 | unbound | all versions | — |
| Debian:13 | unbound | before 1.26.1-0+deb13u1 | 1.26.1-0+deb13u1 |
| Debian:14 | unbound | before 1.25.2-1 | 1.25.2-1 |
| openSUSE:Leap 16.0 | unbound | before 1.25.2-160000.1.1 | 1.25.2-160000.1.1 |
| openSUSE:Tumbleweed | unbound | before 1.25.2-1.1 | 1.25.2-1.1 |
| Red Hat:enterprise_linux:10.2 | python3-unbound | before 0:1.24.2-7.el10_2.4 | 0:1.24.2-7.el10_2.4 |
| Red Hat:enterprise_linux:10.2 | python3-unbound-debuginfo | before 0:1.24.2-7.el10_2.4 | 0:1.24.2-7.el10_2.4 |
+44
Same product
nlnetlabs: all recordsOther highest-scoring records for the same primary product.
- CVE-2019-25042Unbound before 1.9.5 allows an out-of-bounds write via a compressed name in rdata_copy.40Plan
- CVE-2019-25039Unbound before 1.9.5 allows an integer overflow in a size calculation in respip/respip.c.40Plan
- CVE-2019-25038Unbound before 1.9.5 allows an integer overflow in a size calculation in dnscrypt/dnscrypt.c.40Plan
- CVE-2019-25035Unbound before 1.9.5 allows an out-of-bounds write in sldns_bget_token_par.40Plan
- CVE-2019-25034Unbound before 1.9.5 allows an integer overflow in sldns_str2wire_dname_buf_origin, leading to an out-of-bounds write.40Plan
- CVE-2019-25033Unbound before 1.9.5 allows an integer overflow in the regional allocator via the ALIGN_UP macro.40Plan
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| NLnet Labs Unbound | 1.25.2 | Vendor (CNA) |
| azl3 unbound 1.25.1-1 on Azure Linux 3.0 | 1.25.2-1 · CBL-Mariner Releases | Microsoft (MSRC) |
| almalinux:python3-unbound | 1.16.2-5.14.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:unbound | 1.16.2-5.14.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:unbound-anchor | 1.24.2-7.el10_2.4 · AlmaLinux:10 | Package registry (OSV) |
| almalinux:unbound-devel | 1.16.2-5.14.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:unbound-dracut | 1.24.2-3.el9_8.4 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:unbound-libs | 1.16.2-5.14.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:unbound-utils | 1.24.2-7.el10_2.4 · AlmaLinux:10 | Package registry (OSV) |
| alpine:unbound | 1.25.2-r0 · Alpine:v3.22 | Package registry (OSV) |
| debian:unbound | 1.26.1-0+deb13u1 · Debian:13 | Package registry (OSV) |
| opensuse:unbound | 1.25.2-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| red hat:python3-unbound | 0:1.25.2-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:python3-unbound-debuginfo | 0:1.16.2-5.14.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:unbound | 0:1.25.2-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:unbound-anchor | 0:1.24.2-7.el10_2.4 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| red hat:unbound-anchor | 0:1.25.2-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:unbound-anchor-debuginfo | 0:1.24.2-7.el10_2.4 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| red hat:unbound-debuginfo | 0:1.16.2-5.14.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:unbound-debugsource | 0:1.16.2-5.14.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:unbound-devel | 0:1.16.2-5.14.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:unbound-devel | 0:1.25.2-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:unbound-dracut | 0:1.24.2-3.el9_8.4 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:unbound-dracut | 0:1.25.2-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:unbound-libs | 0:1.16.2-5.14.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:unbound-libs | 0:1.25.2-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:unbound-libs-debuginfo | 0:1.16.2-5.14.el8_10 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:unbound-munin | 0:1.25.2-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:unbound-utils | 0:1.25.2-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| rocky linux:unbound | 0:1.16.2-5.14.el8_10 · Rocky Linux:8 | Package registry (OSV) |
+1
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-502480 days apartBOGUS configured primary hostname accepted for XFR in auth/rpz zones26Monitor
- CVE-2026-7795556 days apartPossible ZONEMD verification bypass window17Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- high · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- High
- Availability impact
- None
Weakness class (CWE)
CWE-345 · Insufficient Verification of Data AuthenticityCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- JSON Hijacking (aka JavaScript Hijacking)CAPEC-111likelihood: High · High
- Cache PoisoningCAPEC-141likelihood: High · High
- DNS Cache PoisoningCAPEC-142likelihood: High · High
- Content SpoofingCAPEC-148likelihood: Medium · Medium
- Spoofing of UDDI/ebXML MessagesCAPEC-218Medium
- Application API Message Manipulation via Man-in-the-MiddleCAPEC-384Low
- Transaction or Event Tampering via Application API ManipulationCAPEC-385Medium
- Application API Navigation RemappingCAPEC-386Medium
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.