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TI-2026-54407 Aliases CVE-2026-78227GHSA-jwvw-q5m4-rjxh

Use-after-free in DoQ stream output buffer on reset re-transmission

Priority LOW 29CWE-416Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
High · None · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.

Summary

NLnet Labs Unbound 1.22.0 up to and including 1.26.1, has a use-after-free vulnerability when compiled for DNS-over-QUIC support with '--with-libngtcp2'. Each DoQ stream owns an output buffer that holds the DNS response. ngtcp2's retransmission buffer keeps a shallow pointer into the output buffer for as long as a STREAM frame may be resent. On a client RESET_STREAM, the output buffer is freed but ngtcp2 still holds the matching retransmission entries. The next PTO timeout makes ngtcp2 re-encode the STREAM frame and copy from the freed buffer. A malicious actor that can query Unbound over DoQ and that withholds ACKs, sends RESET_STREAM, and waits for PTO, reaches this use-after-free with no privilege. This leads to retransmissions against freed memory and eventually an abnormal server exit under a 20-query spray.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0034 27th percentileScored 2026-11-07
Fix Fixed Unbound (NLnet Labs): 1.26.1Red Hat: 1 advisory

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

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 LabsUnbound1.22.0 to before 1.26.11.26.1Patch availableCNA
  • Unbound VendorNLnet Labs Affected 1.22.0 to before 1.26.1 Fixed in 1.26.1 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*1.22.0 to before 1.26.1VulnerableNLNETLABS
  • cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:* Versions 1.22.0 to before 1.26.1 Vulnerable ·NLNETLABS

Remediation

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

Red Hat 1 advisory

  • 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-2026-56302 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEYPriority MEDIUM 49
    • 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
    Show all 9 records →

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat Hardened ImagesFixed RHSA-2026:68590
Not affected: 7 products
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9
  • Red Hat OpenShift Container Platform 4
  • Red Hat OpenShift Container Platform 5

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-78227
  2. 2026-10-03 Alias added: GHSA-jwvw-q5m4-rjxh
  3. 2026-11-06 Affected versions changed · Red Hat

References

Patch 1

  • TI-2026-25690 Possible arbitrary code execution during DNSSEC validation CVSS 4.0CRITICAL 9.1
  • TI-2026-56302 Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY 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
See all 96 →

Sources

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