Bug 2573426 (CVE-2026-128089)

Summary: CVE-2026-128089 dnspython: dnspython: Denial of Service via large service numbers in WKS records
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in dnspython. An attacker can cause a Denial of Service (DoS) by supplying a maliciously crafted Domain Name System (DNS) zone file. The Well-Known Service (WKS) record parser fails to validate that service numbers fall within the expected range before using them as bitmap offsets. Processing an excessively large service number causes the parser to repeatedly allocate memory, consuming excessive CPU and memory resources and potentially terminating the process.
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Description OSIDB Bzimport 2026-11-13 19:31:20 UTC 
dnspython is a DNS toolkit for Python. Prior to version 2.9.2, the from_text() parser for WKS records does not require the service number to be between 0 and 65535 before using it as a bitmap offset. An attacker-controlled zone file can supply a larger number, causing the service bitmap to grow to an extremely large size through inefficient repeated extension, consuming excessive memory and CPU and potentially terminating the process. Applications are affected only when they parse zone-file text whose record type and rdata are attacker controlled. This issue is fixed in version 2.9.2.