SB2026051245 - Multiple vulnerabilities in Dnsmasq

CSH
CYBERSECURITY HELP
Sign In REGISTER

Main Vulnerability Database SB2026051245

SB2026051245 - Multiple vulnerabilities in Dnsmasq

Published: May 12, 2026

Security Bulletin ID SB2026051245
CSH Severity
High
Patch available
YES
Number of vulnerabilities 6
Exploitation vector Remote access
Highest impact Code execution

Breakdown by Severity

High 17% Medium 83%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 6 vulnerabilities.


1) Out-of-bounds write (CVE-ID: CVE-2026-2291)

CWE-ID: CWE-787 - Out-of-bounds write

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green


The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to out-of-bounds write in struct bigname when processing DNS queries or DNS responses containing large domain names. A remote attacker can send a specially crafted DNS query or response to cause a denial of service.


2) Input validation error (CVE-ID: CVE-2026-4890)

CWE-ID: CWE-20 - Improper input validation

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green


The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to improper input validation in NSEC bitmap parsing in dnssec.c when processing crafted DNSSEC NSEC or NSEC3 records. A remote attacker can send a specially crafted DNS response to cause a denial of service.

No valid DNSSEC signatures are needed because the issue is reachable before RRSIG validation.


3) Out-of-bounds read (CVE-ID: CVE-2026-5172)

CWE-ID: CWE-125 - Out-of-bounds read

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green


The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to out-of-bounds read in extract_addresses() when parsing a DNS resource record with a falsified rdlen value. A remote attacker can send a specially crafted DNS packet to cause a denial of service.

The issue occurs because extract_name() can advance the record pointer past the calculated end of the resource record, causing the remaining-length calculation to underflow.


4) Input validation error (CVE-ID: CVE-2026-4893)

CWE-ID: CWE-20 - Improper input validation

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green


The vulnerability allows a remote attacker to bypass client subnet source validation.

The vulnerability exists due to improper input validation in check_source() handling in process_reply() when processing DNS replies with the --add-subnet feature enabled. A remote attacker can send a specially crafted DNS reply to bypass client subnet source validation.

Only configurations with --add-subnet enabled are vulnerable.


5) Stack-based buffer overflow (CVE-ID: CVE-2026-4892)

CWE-ID: CWE-121 - Stack-based buffer overflow

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber


The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to stack-based buffer overflow in helper.c when processing oversized DHCPv6 CLIDs for the --dhcp-script helper path. A remote attacker can send a specially crafted DHCPv6 client identifier to execute arbitrary code.

Only configurations with --dhcp-script enabled are vulnerable, and the helper process retains root privileges.


6) Input validation error (CVE-ID: CVE-2026-4891)

CWE-ID: CWE-20 - Improper input validation

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green


The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to improper input validation in RRSIG packet handling in dnssec.c when processing crafted RRSIG records with an undersized rdlen value. A remote attacker can send a specially crafted DNS response to cause a denial of service.


Remediation

Install update from vendor's website.

References