CVE-2026-18739 Red Hat CVE debrief

Who should care

System administrators and developers using the popt library should care about this vulnerability, especially in applications that handle untrusted input or operate in environments where local attackers may be present. Affected operators include system administrators, developers, and security teams responsible for vulnerability management and patching. The vulnerability-management impact involves assessing and prioritizing patching based on environment impact, while the security-team impact involves monitoring for local exploitation attempts and verifying affected scope and severity.

Technical summary

The popt library, used for command-line option parsing, contains an off-by-one error in the poptStuffArgs function. This error, when repeatedly called by a host application or through deep alias nesting, can lead to corruption of internal program data. If a host application then processes this altered data unsafely, it could potentially allow a local attacker to execute arbitrary code. The affected product context involves applications using the popt library, especially those handling untrusted input or operating in environments where local attackers may be present. Defensive impact includes prioritizing patching based on environment impact and monitoring for local exploitation attempts.

Defensive priority

Local attackers may exploit this vulnerability to execute arbitrary code. Assess and prioritize patching based on environment impact.

Recommended defensive actions

• Inventory and assess systems using the popt library for exposure
• Prioritize patching based on environment impact
• Monitor for local exploitation attempts
• Apply vendor patches or updates for the popt library
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE-2026-18739 record indicates an off-by-one error in the poptStuffArgs function of the popt library, which can lead to internal program data corruption. This corruption could potentially enable a local attacker to execute arbitrary code if the host application then unsafely processes the altered data. The CVSS score is 2.5, with a LOW severity. Red Hat has a reference for this CVE.

Official resources