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TI-2026-56302 Aliases CVE-2026-81642GHSA-xxc4-rpp8-3fw7

Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY

Priority MEDIUM 49CWE-122Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 18 fixed, 1 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-122 and the CVSS impact.

Summary

In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in the DNSSEC validator that enables denial of service and possible remote code execution as a result of digesting DNSKEYs. A DNSKEY with an owner compression pointer to its own RDATA can overflow the digest buffer. Remote code execution is possible through attacker controlled data. An adversary can exploit the vulnerability by controlling a malicious zone and querying a vulnerable Unbound.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00962 61st percentileScored 2026-11-07
Fix Partial Unbound (NLnet Labs): 1.26.1Red Hat: 12 advisoriesRed Hat: 18 fixed, 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
NLnet LabsUnboundbefore 1.26.11.26.1Patch availableCNA
  • Unbound VendorNLnet Labs Affected before 1.26.1 Fixed in 1.26.1 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*before 1.26.1VulnerableNLNETLABS
  • cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:* Versions before 1.26.1 Vulnerable ·NLNETLABS

Remediation

  • Fix · CNA Unbound (NLnet Labs) Fixed in 1.26.1

Red Hat 12 advisories

  • RHSA-2026:72264 Released 2026-09-27 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream E4S (v.8.8) python3-unbound-1.16.2-5.el8_8.6, unbound-1.16.2-5.el8_8.6, unbound-devel-1.16.2-5.el8_8.6 +1
    • Red Hat Enterprise Linux AppStream TUS (v.8.8) python3-unbound-1.16.2-5.el8_8.6, unbound-1.16.2-5.el8_8.6, unbound-devel-1.16.2-5.el8_8.6 +1
  • RHSA-2026:72199 Released 2026-09-26 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux Server (v. 7 ELS) unbound-1.6.6-5.el7_9.2, unbound-libs-1.6.6-5.el7_9.2, unbound-libs-1.6.6-5.el7_9.2.ppc
    • Red Hat Enterprise Linux Server Optional (v. 7 ELS) unbound-devel-1.6.6-5.el7_9.2, unbound-devel-1.6.6-5.el7_9.2.ppc, unbound-python-1.6.6-5.el7_9.2
  • RHSA-2026:72183 Released 2026-09-25 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.4) unbound-1.7.3-15.el8_4.4, unbound-libs-1.7.3-15.el8_4.4
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) unbound-1.7.3-15.el8_4.4, unbound-libs-1.7.3-15.el8_4.4
Show 9 more Red Hat advisories
  • RHSA-2026:72110 Released 2026-09-25 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.6) unbound-1.7.3-17.el8_6.8, unbound-libs-1.7.3-17.el8_6.8
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) unbound-1.7.3-17.el8_6.8, unbound-libs-1.7.3-17.el8_6.8
  • RHSA-2026:71487 Released 2026-09-24 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream (v. 9) python3-unbound-1.24.2-3.el9_8.8, unbound-1.24.2-3.el9_8.8, unbound-dracut-1.24.2-3.el9_8.8 +1
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) unbound-devel-1.24.2-3.el9_8.8
  • RHSA-2026:71610 Released 2026-09-24 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.2) python3-unbound-1.16.2-3.el9_2.6, unbound-1.16.2-3.el9_2.6, unbound-libs-1.16.2-3.el9_2.6
  • RHSA-2026:71611 Released 2026-09-24 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.4) python3-unbound-1.16.2-8.el9_4.3, unbound-1.16.2-8.el9_4.3, unbound-libs-1.16.2-8.el9_4.3
  • RHSA-2026:71460 Released 2026-09-24 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) unbound-1.16.2-19.el9_6.2, unbound-libs-1.16.2-19.el9_6.2
  • RHSA-2026:71419 Released 2026-09-24 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream (v. 10) python3-unbound-1.24.2-7.el10_2.6, unbound-1.24.2-7.el10_2.6, unbound-anchor-1.24.2-7.el10_2.6 +3
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) unbound-devel-1.24.2-7.el10_2.6
  • RHSA-2026:71459 Released 2026-09-24 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) unbound-1.20.0-18.el10_0.13, unbound-libs-1.20.0-18.el10_0.13
  • RHSA-2026:70754 Released 2026-09-23 · Red Hat rating Critical
    unbound security update
    • Red Hat Enterprise Linux AppStream (v. 8) python3-unbound-1.16.2-5.14.el8_10.4, unbound-1.16.2-5.14.el8_10.4, unbound-devel-1.16.2-5.14.el8_10.4 +1
  • RHSA-2026:68590 Released 2026-09-17 · Red Hat rating Critical
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images python3-unbound-1.26.1-1.hum1@aarch64, python3-unbound-1.26.1-1.hum1@x86_64, unbound-1.26.1-1.hum1@aarch64 +14

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    NLnet Labs Unbound 1.26.1

    9 records Highest priority Priority MEDIUM 2 MEDIUM, 7 LOW

    Other records, highest priority first

    • TI-2026-57038 CNAME synthesis could lead to heap corruptionPriority MEDIUM 40
    • TI-2026-58665 Retrap: Novel Vulnerabilities to launch Algorithmic Complexity Attacks on DNSSECPriority LOW 39
    • TI-2026-56296 Possible heap buffer overflow during DNSSEC canonicalizationPriority LOW 39
    Show all 9 records →

Vendor assessments

Red Hat

Red Hat rating: Critical. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:71419
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2026:70754
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:71487
Red Hat Enterprise Linux AppStream AUS (v.8.4)Fixed RHSA-2026:72183
Red Hat Enterprise Linux AppStream AUS (v.8.6)Fixed RHSA-2026:72110
Red Hat Enterprise Linux AppStream E4S (v.8.8)Fixed RHSA-2026:72264
Red Hat Enterprise Linux AppStream E4S (v.9.2)Fixed RHSA-2026:71610
Red Hat Enterprise Linux AppStream E4S (v.9.4)Fixed RHSA-2026:71611
Red Hat Enterprise Linux AppStream EUS (v. 10.0)Fixed RHSA-2026:71459
Red Hat Enterprise Linux AppStream EUS (v.9.6)Fixed RHSA-2026:71460
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)Fixed RHSA-2026:72183
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)Fixed RHSA-2026:72110
Red Hat Enterprise Linux AppStream TUS (v.8.8)Fixed RHSA-2026:72264
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)Fixed RHSA-2026:71419
Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)Fixed RHSA-2026:71487
Red Hat Enterprise Linux Server (v. 7 ELS)Fixed RHSA-2026:72199
Red Hat Enterprise Linux Server Optional (v. 7 ELS)Fixed RHSA-2026:72199
Red Hat Hardened ImagesFixed RHSA-2026:68590
Not affected: 10 products
  • Red Hat CodeReady Linux Builder EUS (v.9.6)
  • Red Hat Enterprise Linux AppStream AUS (v.8.4)
  • Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0)
  • Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0)
  • Red Hat OpenShift Container Platform 4
  • Red Hat OpenShift Container Platform 5

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-81642
  2. 2026-10-03 Alias added: GHSA-xxc4-rpp8-3fw7
  3. 2026-11-03 Affected versions changed · Red Hat

References

Patch 1

  • TI-2026-25690 Possible arbitrary code execution during DNSSEC validation CVSS 4.0CRITICAL 9.1
  • TI-2026-31146 Crash during DNSSEC validation of malicious content CVSS 4.0HIGH 8.7
  • TI-2026-31135 Heap overflow with multiple NSID, COOKIE, PADDING EDNS options CVSS 4.0HIGH 8.7
  • TI-2026-36436 Routinator crashes on specifically crafted RRDP XML files CVSS 4.0HIGH 8.7
  • TI-2026-36433 Routinator exits when accepting an incoming HTTP or RTR connection fails CVSS 4.0HIGH 8.7
  • TI-2026-10532 Denial of DNS over TLS service by any DoT client CVSS 4.0HIGH 8.7
See all 96 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences