Hi there, (The official announcement and more information can be found at: https://nlnetlabs.nl/news/2025/Nov/26/unbound-1.24.2-released/)
We were made aware that previous fixes for CVE-2025-11411 released with Unbound 1.24.1 were not complete. Namely, Unbound is still vulnerable if the response would be YXDOMAIN or nodata non-referral, together with promiscuous (possibly poisonous) NS RRSets. We are releasing 1.24.2 as a security release on the 26th of November including the relevant fix. == Summary (Same as CVE-2025-11411) Promiscuous NS RRSets that complement DNS replies in the authority section can be used to trick resolvers to update their delegation information for the zone. Usually these RRSets are used to update the resolver's knowledge of the zone's name servers. If a malicious actor is able to attach such records in a reply (i.e., spoofed packet, fragmentation attack) he would be able to poison Unbound's cache for the delegation point. Unbound 1.24.1 includes a fix to mitigate the poison attempt. Unbound 1.24.2 will include an additional fix to mitigate the poison attempt through YXDOMAIN and nodata non-referral answers. == Affected products Unbound up to and including version 1.24.1. == Description (Same as CVE-2025-11411) A malicious actor can exploit the possible poisonous effect by injecting NS RRSets (and possibly their respective address records) in a reply. This could be done for example by trying to spoof a packet or fragmentation attacks. Unbound would then proceed to update the NS RRSet data it already has since the new data has enough trust for it, i.e., in-zone data for the delegation point. Unbound 1.24.1 includes a fix that scrubs unsolicited NS RRSets (and their respective address records) from replies mitigating the possible poison effect. Unbound 1.24.2 will include an additional fix to apply the same scrubbing of unsolicited NS RRSets (and their respective address records) also for YXDOMAIN and nodata non-referral answers. == Mitigation Unbound 1.24.2 fully addresses the vulnerability. The mitigation section of the authoritative text for CVE-2025-11411 (https://nlnetlabs.nl/downloads/unbound/CVE-2025-11411.txt)contains links to patches and instructions if you need to patch your current version.
== Acknowledgements We would like to thank TaoFei Guo from Peking University, Yang Luo and JianJun Chen from Tsinghua University for discovering and responsibly disclosing the partial mitigation of CVE-2025-11411 in the previous Unbound version. ** This email is signed. Keys of the NLnet Labs people are published on https://www.nlnetlabs.nl/people/ ** Best regards, -- Yorgos
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