# CVE-2023-31137: maradns: MaraDNS is open-source software that implements the Domain Name System (DNS)

CVE-2023-31137 is fixed in 5 products on 1 platform, first by duende 2.0.13-1.2ubuntu0.1~esm1, released May 9, 2023. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2023-31137
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0114
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 9, 2023

## Description

MaraDNS is open-source software that implements the Domain Name System (DNS). In version 3.5.0024 and prior, a remotely exploitable integer underflow vulnerability in the DNS packet decompression function allows an attacker to cause a Denial of Service by triggering an abnormal program termination.  The vulnerability exists in the `decomp_get_rddata` function within the `Decompress.c` file. When handling a DNS packet with an Answer RR of qtype 16 (TXT record) and any qclass, if the `rdlength` is smaller than `rdata`, the result of the line `Decompress.c:886` is a negative number `len = rdlength - total;`. This value is then passed to the `decomp_append_bytes` function without proper validation, causing the program to attempt to allocate a massive chunk of memory that is impossible to allocate. Consequently, the program exits with an error code of 64, causing a Denial of Service.  One proposed fix for this vulnerability is to patch `Decompress.c:887` by breaking `if(len <= 0)`, which has been incorporated in version 3.5.0036 via commit bab062bde40b2ae8a91eecd522e84d8b993bab58.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | duende Ubuntu 18.04.6 LTS (bionic) | 2.0.13-1.2ubuntu0.1~esm1 | [duende 2.0.13-1.2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-duende-2.0.13-1.2ubuntu0.1-esm1.md) | May 9, 2023 |
| Linux | duende Ubuntu 20.04 LTS (focal) | 2.0.13-1.4+deb11u1build0.20.04.1 | [duende 2.0.13-1.4+deb11u1build0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-duende-2.0.13-1.4-deb11u1build0.20.04.1.md) | May 9, 2023 |
| Linux | duende Ubuntu 22.04.1 LTS (jammy) | 2.0.13-1.4+deb11u1build0.22.04.1 | [duende 2.0.13-1.4+deb11u1build0.22.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-duende-2.0.13-1.4-deb11u1build0.22.04.1.md) | May 9, 2023 |
| Linux | maradns Debian 11.6 (bullseye) | 2.0.13-1.4+deb11u1 | [DEBIAN-CVE-2023-31137](https://patchblox.com/security/data/fix/linux/debian-cve-2023-31137.md) | May 9, 2023 |
| Linux | maradns Ubuntu 18.04.6 LTS (bionic) | 2.0.13-1.2ubuntu0.1~esm1 | [maradns 2.0.13-1.2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-maradns-2.0.13-1.2ubuntu0.1-esm1.md) | May 9, 2023 |
| Linux | maradns Ubuntu 20.04 LTS (focal) | 2.0.13-1.4+deb11u1build0.20.04.1 | [maradns 2.0.13-1.4+deb11u1build0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-maradns-2.0.13-1.4-deb11u1build0.20.04.1.md) | May 9, 2023 |
| Linux | maradns Ubuntu 22.04.1 LTS (jammy) | 2.0.13-1.4+deb11u1build0.22.04.1 | [maradns 2.0.13-1.4+deb11u1build0.22.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-maradns-2.0.13-1.4-deb11u1build0.22.04.1.md) | May 9, 2023 |
| Linux | maradns-deadwood Ubuntu 18.04.6 LTS (bionic) | 2.0.13-1.2ubuntu0.1~esm1 | [maradns-deadwood 2.0.13-1.2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-maradns-deadwood-2.0.13-1.2ubuntu0.1-esm1.md) | May 9, 2023 |
| Linux | maradns-deadwood Ubuntu 20.04 LTS (focal) | 2.0.13-1.4+deb11u1build0.20.04.1 | [maradns-deadwood 2.0.13-1.4+deb11u1build0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-maradns-deadwood-2.0.13-1.4-deb11u1build0.20.04.1.md) | May 9, 2023 |
| Linux | maradns-deadwood Ubuntu 22.04.1 LTS (jammy) | 2.0.13-1.4+deb11u1build0.22.04.1 | [maradns-deadwood 2.0.13-1.4+deb11u1build0.22.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-maradns-deadwood-2.0.13-1.4-deb11u1build0.22.04.1.md) | May 9, 2023 |
| Linux | maradns-docs Ubuntu 18.04.6 LTS (bionic) | 2.0.13-1.2ubuntu0.1~esm1 | [maradns-docs 2.0.13-1.2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-maradns-docs-2.0.13-1.2ubuntu0.1-esm1.md) | May 9, 2023 |
| Linux | maradns-docs Ubuntu 20.04 LTS (focal) | 2.0.13-1.4+deb11u1build0.20.04.1 | [maradns-docs 2.0.13-1.4+deb11u1build0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-maradns-docs-2.0.13-1.4-deb11u1build0.20.04.1.md) | May 9, 2023 |
| Linux | maradns-docs Ubuntu 22.04.1 LTS (jammy) | 2.0.13-1.4+deb11u1build0.22.04.1 | [maradns-docs 2.0.13-1.4+deb11u1build0.22.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-maradns-docs-2.0.13-1.4-deb11u1build0.22.04.1.md) | May 9, 2023 |
| Linux | maradns-zoneserver Ubuntu 18.04.6 LTS (bionic) | 2.0.13-1.2ubuntu0.1~esm1 | [maradns-zoneserver 2.0.13-1.2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-maradns-zoneserver-2.0.13-1.2ubuntu0.1-esm1.md) | May 9, 2023 |
| Linux | maradns-zoneserver Ubuntu 20.04 LTS (focal) | 2.0.13-1.4+deb11u1build0.20.04.1 | [maradns-zoneserver 2.0.13-1.4+deb11u1build0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-maradns-zoneserver-2.0.13-1.4-deb11u1build0.20.04.1.md) | May 9, 2023 |
| Linux | maradns-zoneserver Ubuntu 22.04.1 LTS (jammy) | 2.0.13-1.4+deb11u1build0.22.04.1 | [maradns-zoneserver 2.0.13-1.4+deb11u1build0.22.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-maradns-zoneserver-2.0.13-1.4-deb11u1build0.22.04.1.md) | May 9, 2023 |

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