CVE-2026-55991
CVE-2026-55991: 1 tracked advisory record across Red Hat. Compare source-reported impact, fixes and remediation.
Compare the source-linked records below. Ratings and product/version details belong to each advisory; they are not a single CVE-wide score or proof that every listed product is affected. How VulniPulse collects and checks evidence.
Vendor advisory comparison
Red Hat
1 advisory- Advisory severityMedium5.9
Medium [CVE-2026-55991] Denial of Service via crafted DNS-over-QUIC connection
CVE-2026-55991Source published Source updated
In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, a remote unauthenticated client can trigger a libngtcp2 assertion (if compiled with assertions on) and terminate the entire Unbound process using a single DNS-over-QUIC (DoQ) connection and one normal DNS query. This is caused by an erroneous error value passed to libngtcp2. When 'ngtcp2_conn_writev_stream()' returns 'NGTCP2_ERR_STREAM_DATA_BLOCKED', Unbound continues to call 'ngtcp2_ccerr_set_application_error()' with a '-1' error value. The 'int' literal '-1' is implicitly converted to the function's 'uint64_t error_code' parameter as '0xFFFFFFFFFFFFFFFF'. The follow-on 'ngtcp2_conn_write_connection_close()' serialises that value as a QUIC variable-length integer; because '2^64-1' exceeds the 62-bit varint ceiling…
- Affected products in this advisory
- Red Hat Hardened Images
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4
1 more entries in the full advisory.
- Source-reported affected versions
- 1.22.0
- 1.25.1
- Source-reported fixed versions
- unbound-main-1.25.2-0.1.hum1
- RHSA-2026:43588
- Mitigation guidance
- To prevent exploitation, disable DNS-over-QUIC (DoQ) functionality within Unbound if it is not actively used. This typically involves adjusting Unbound's configuration to remove or comment out DoQ-related listening directives. After modifying the configuration, restart the Unbound service for the changes to take effect.
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