Bug 2491663 (CVE-2026-12969)

Summary: CVE-2026-12969 dnsmasq: dnsmasq: out-of-bounds read in find_soa() due to missing extrabytes validation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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An out-of-bounds read vulnerability exists in dnsmasq's find_soa() function in src/rfc1035.c. When parsing NS section records, extract_name() is called with extrabytes=0, failing to validate that 10 additional bytes exist for fixed-length DNS record fields. A remote attacker controlling a DNS zone can exploit this via a crafted NXDOMAIN response to cause a 10-byte heap out-of-bounds read, potentially accessing stale data from prior transactions.
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Bug Depends On: 2491687    
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Description OSIDB Bzimport 2026-06-23 09:43:58 UTC 
An out-of-bounds read vulnerability was found in dnsmasq's find_soa() function in src/rfc1035.c. The function calls extract_name() with extrabytes=0 when parsing NS section records in NXDOMAIN/NODATA responses, which only validates that the DNS name fits within the packet but does not verify that 10 additional bytes exist for the fixed-length fields (type, class, TTL, rdlen). The subsequent GETSHORT/GETLONG macros then unconditionally read 10 bytes past the valid packet boundary.

An attacker controlling a DNS zone can trigger this by returning a crafted NXDOMAIN response where the NS record name (a compression pointer) extends to the packet boundary. The 10-byte over-read typically stays within dnsmasq's over-allocated packet buffer (headroom of 1035 bytes), limiting crash risk, but accesses data outside the logical packet boundary and may read stale heap data from prior DNS transactions.

Upstream fix: https://repo.or.cz/dnsmasq.mirror.git/commit/14094e88beca519c53151184cc4553656672b54f Fixed in: dnsmasq 2.93rc1