CVE-2026-102559 Red Hat CVE debrief

Who should care

Defenders responsible for systems using libsoup, especially in WebSocket-enabled applications, should assess exposure and prioritize remediation. Red Hat Enterprise Linux users should review and apply relevant errata.

Why it matters

CVE-2026-102559 is a heap buffer overflow vulnerability in libsoup that could impact systems using affected versions, particularly those with WebSocket functionality. Defenders should assess exposure, prioritize remediation, and monitor for potential exploitation attempts.

• Potential for heap buffer overflow leading to denial of service or code execution
• Requires verification of affected libsoup versions in system inventory
• Remediation priority for systems using vulnerable libsoup versions
• Monitoring for exploitation attempts may be necessary

Technical summary

The libsoup library is vulnerable to a heap buffer overflow when constructing masked WebSocket client frames for large outgoing payloads. This occurs because size values passed to GByteArray allocation APIs could be truncated, while the masking routine still uses the full length. The vulnerability can be mitigated by reviewing and applying Red Hat errata RHSA-2026:83384, RHSA-2026:83618, and RHSA-2026:84586 as needed. Defenders should prioritize assessment and remediation of this vulnerability, especially in systems using libsoup for WebSocket functionality.

Defensive priority

Defenders should prioritize assessment and remediation of this vulnerability, especially in systems using libsoup for WebSocket functionality.

Recommended defensive actions

• Assess exposure to CVE-2026-102559, especially in systems using libsoup for WebSocket functionality
• Review and apply Red Hat errata RHSA-2026:83384, RHSA-2026:83618, and RHSA-2026:84586 as needed
• Verify system inventory for affected libsoup versions and prioritize remediation
• Monitor for potential exploitation attempts targeting this vulnerability
• Implement 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 record and NVD detail page provide information on the vulnerability. Red Hat has released several errata addressing this issue, indicating potential impact on Red Hat Enterprise Linux systems.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.