High [CVE-2026-6949] TSIG packet with crafted name compression can crash DNS server
This high-severity Red Hat Linux advisory covers CVE-2026-6949.
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Summary
A flaw was found in Samba's internal DNS server when processing TSIG-signed DNS packets containing compressed names. Incorrect size calculations while determining the portion of the DNS packet covered by the TSIG signature can result in an integer underflow, leading to an out-of-bounds memory write during packet processing.
A remote attacker can send a specially crafted TSIG-signed DNS packet to cause the DNS server to terminate unexpectedly. Red Hat Product Security evaluates this vulnerability as having an Important impact for Samba deployments operating as an Active Directory Domain Controller (AD DC) using the internal DNS server engine.
``` Red Hat Enterprise Linux (RHEL) Context: Default installations of Red Hat Enterprise Linux (RHEL) are not affected. RHEL does not ship or support the Samba Active Directory Domain Controller (AD DC) role or its internal DNS server component where this vulnerability resides.
``` ``` Additionally, Samba AD DC deployments that use the external BIND9 DLZ plugin instead of the internal DNS server engine are completely unaffected by this issue. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-787.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 9 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 9 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 9 days ago·verify at source
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