# CVE-2026-81928: libnet-dns-perl: Net::DNS versions before 1.57 for Perl allow memory exhaustion via unbounded recursion in sig_data when re-encoding a... CVE-2026-81928 is fixed in 4 products on 1 platform, first by DEBIAN-CVE-2026-81928, released September 7, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-81928 - Priority: High - CVSS: 7.5 (high) - EPSS: 0.0068 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Sep 2, 2026 ## Description Net::DNS versions before 1.57 for Perl allow memory exhaustion via unbounded recursion in sig_data when re-encoding a message with a misplaced TSIG record. sig_data signs a message by re-encoding it, and removes TSIG records only from the additional section. A TSIG decoded into the answer or authority section survives that step and is signed again, so encoding re-enters sig_data with no termination condition. Decoding does not reject such a message: a TSIG that is not the last record on the wire raises "misplaced or corrupt TSIG", but the error is caught, reported as a warning, and the record is left in the packet. RFC 8945 section 5.2 requires the message to be dropped. The recursion is reached only when the decoded TSIG carries an empty MAC, since a MAC recovered from the wire short-circuits the signing step. It is reached only from code that re-encodes a message it decoded, such as a forwarder or a proxy. A decoded message that is never re-encoded is unaffected. Message direction does not matter: a query reaches the same path as a response. Each cycle re-encodes the whole message, so fewer than 100 bytes on the wire exhaust available memory and terminate the process. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | libnet-dns-perl Debian 14 | 1.57-1 | [DEBIAN-CVE-2026-81928](https://patchblox.com/security/data/fix/linux/debian-cve-2026-81928.md) | Sep 7, 2026 | | Linux | perl-Net-DNS Fedora 43 | 1.57-1.fc43 | [FEDORA-2026-48A4531E02](https://patchblox.com/security/data/fix/linux/fedora-2026-48a4531e02.md) | Sep 14, 2026 | | Linux | perl-Net-DNS RHEL 8 | 0:1.15-2.el8_10 | [RHSA-2026:68787](https://patchblox.com/security/data/fix/linux/rhsa-2026-68787.md) | Sep 19, 2026 | | Linux | perl-Net-DNS RHEL 9 | 0:1.29-6.el9_8.1 | [RHSA-2026:68786](https://patchblox.com/security/data/fix/linux/rhsa-2026-68786.md) | Sep 19, 2026 | | Linux | perl-Net-DNS almalinux 8 | 1.15-2.el8_10 | [ALSA-2026:68787](https://patchblox.com/security/data/fix/linux/alsa-2026-68787.md) | Sep 17, 2026 | | Linux | perl-Net-DNS almalinux 9 | 1.29-6.el9_8.1 | [ALSA-2026:68786](https://patchblox.com/security/data/fix/linux/alsa-2026-68786.md) | Sep 17, 2026 | | Linux | perl-Net-DNS amzn 2023 | 1.57-1.amzn2023.0.1 | [ALAS2023-2026-3094](https://patchblox.com/security/data/fix/linux/alas2023-2026-3094.md) | Sep 28, 2026 | | Linux | perl-Net-DNS ol 8 | 0:1.15-2.el8_10 | [ELSA-2026-68787](https://patchblox.com/security/data/fix/linux/elsa-2026-68787.md) | Sep 17, 2026 | | Linux | perl-Net-DNS ol 9 | 0:1.29-6.el9_8.1 | [ELSA-2026-68786](https://patchblox.com/security/data/fix/linux/elsa-2026-68786.md) | Sep 17, 2026 | | Linux | perl-Net-DNS opensuse-leap 16.0 | 1.570.0-bp160.1.1 | [OPENSUSE-SU-2026:21859-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21859-1.md) | Sep 15, 2026 | | Linux | perl-Net-DNS rocky 8 | 0:1.15-2.el8_10 | [RLSA-2026:68787](https://patchblox.com/security/data/fix/linux/rlsa-2026-68787.md) | Sep 19, 2026 | | Linux | perl-Net-DNS rocky 9 | 0:1.29-6.el9_8.1 | [RLSA-2026:68786](https://patchblox.com/security/data/fix/linux/rlsa-2026-68786.md) | Sep 19, 2026 | | Linux | perl-Net-DNS sles 15.7 | 1.14-150000.3.6.1 | [SUSE-SU-2026:4086-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4086-1.md) | Sep 8, 2026 | | Linux | perl-Net-DNS-Nameserver Fedora 43 | 1.57-1.fc43 | [FEDORA-2026-48A4531E02](https://patchblox.com/security/data/fix/linux/fedora-2026-48a4531e02.md) | Sep 14, 2026 | | Linux | perl-Net-DNS-Nameserver RHEL 9 | 0:1.29-6.el9_8.1 | [RHSA-2026:68786](https://patchblox.com/security/data/fix/linux/rhsa-2026-68786.md) | Sep 19, 2026 | | Linux | perl-Net-DNS-Nameserver almalinux 9 | 1.29-6.el9_8.1 | [ALSA-2026:68786](https://patchblox.com/security/data/fix/linux/alsa-2026-68786.md) | Sep 17, 2026 | | Linux | perl-Net-DNS-Nameserver amzn 2023 | 1.57-1.amzn2023.0.1 | [ALAS2023-2026-3094](https://patchblox.com/security/data/fix/linux/alas2023-2026-3094.md) | Sep 28, 2026 | | Linux | perl-Net-DNS-Nameserver ol 9 | 0:1.29-6.el9_8.1 | [ELSA-2026-68786](https://patchblox.com/security/data/fix/linux/elsa-2026-68786.md) | Sep 17, 2026 | | Linux | perl-Net-DNS-tests Fedora 43 | 1.57-1.fc43 | [FEDORA-2026-48A4531E02](https://patchblox.com/security/data/fix/linux/fedora-2026-48a4531e02.md) | Sep 14, 2026 | | Linux | perl-Net-DNS-tests amzn 2023 | 1.57-1.amzn2023.0.1 | [ALAS2023-2026-3094](https://patchblox.com/security/data/fix/linux/alas2023-2026-3094.md) | Sep 28, 2026 | --- Data as of 2026-11-09T13:31:49Z UTC. 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