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Tag: denial-of-service

CVE-2026-76418: Cisco Secure Firewall ASA/FTD Denial of Service Vulnerability

Posted on November 3, 2026 by Kyle

Overview

CVE-2026-76418 addresses a critical denial of service vulnerability in Cisco Secure Firewall ASA and FTD Software. An unauthenticated, remote attacker can trigger an unexpected device reload by sending crafted requests to the SSL remote access VPN service. This vulnerability is due to logic errors related to secondary authentication on tunnel groups and is currently listed in CISA’s Known Exploited Vulnerabilities Catalog.

Technical Analysis

A vulnerability in the Remote Access SSL VPN service of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition.

  • Vulnerability Type: Unchecked return value to NULL pointer dereference (CWE-690).
  • Affected Products: Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Secure Firewall Threat Defense (FTD) Software.
  • Attack Vector: Remote Access SSL VPN service.
  • Prerequisites: Secondary authentication must be configured on a tunnel group.
  • Exploitation: An unauthenticated, remote attacker sends a crafted request when connecting to the SSL remote access VPN.
  • Impact: A successful exploit causes the affected device to reload, resulting in a denial of service (DoS) condition.
  • CVSS 3.1 Score: 8.6 (HIGH) – CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Detection

  • Monitor Cisco ASA/FTD device logs for unexpected reloads or crashes, specifically looking for system messages indicating a reload event.
  • Look for an increased volume of failed or abnormal SSL VPN connection attempts preceding a device reload.
  • Analyze network traffic for unusual or malformed SSL VPN connection requests, particularly those targeting devices with secondary authentication configured.
  • Review device uptime and availability metrics for unexpected interruptions.

Sigma Detection Rules

⚠️ AI-generated detection rules. These are experimental starting points. Review field names, EventIDs, and logic against your environment’s schema before deploying. Tune to reduce false positives.

Cisco ASA FTD Unexpected Device Reload

title: Cisco ASA FTD Unexpected Device Reload
id: 90f7a01d-5b3e-4f1c-9e2a-7b8d6c5f4e3c
status: experimental
description: Detects unexpected device reloads in Cisco ASA/FTD logs, indicative of a denial of service condition or system instability.
logsource:
  product: cisco
  service: asa
detection:
  selection:
    message|contains:
      - 'Reloading due to'
      - 'System is restarting'
      - 'Device rebooted unexpectedly'
  condition: selection
level: high

Mitigations

  1. Apply security patches from Cisco as soon as they become available. (As of the NVD publication date, the vulnerability is undergoing analysis, and patches are anticipated).
  2. Review configurations of SSL remote access VPN tunnel groups to identify instances where secondary authentication is enabled.
  3. Implement network segmentation to restrict access to the SSL VPN service from untrusted networks where possible.
  4. Ensure robust logging and monitoring are in place for Cisco ASA/FTD devices to detect reloads or suspicious activity.

References

  • https://nvd.nist.gov/vuln/detail/CVE-2026-76418
  • https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-tunnel-dos-s6mgkb75
  • https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-76418
  • https://ltna.com.au/cyber

Indicators of Compromise

No public IOCs available at time of writing.

MITRE ATT&CK

  • T1499 — Endpoint Denial of Service
🤖 AI Attribution
Generated by gemini-2.5-flash ·
1,903 input / 1,133 output tokens ·
Reviewed and approved by a human analyst before publication
Posted in vulnerabilityTagged cisco, denial-of-service, high, network-device, vpn, vulnerabilityLeave a comment

CVE-2026-88779: Citrix NetScaler Denial of Service Vulnerability (CWE-119)

Posted on October 5, 2026 by Kyle

Overview

CVE-2026-88779 is a denial of service (DoS) vulnerability impacting Citrix NetScaler ADC (formerly Citrix ADC) and NetScaler Gateway (formerly Citrix Gateway) products. The flaw stems from an improper restriction of operations within the bounds of a memory buffer (CWE-119). This vulnerability is significant as it affects critical network infrastructure components and is included in CISA’s Known Exploited Vulnerabilities (KEV) catalog, highlighting its potential for active exploitation or high risk.

Technical Analysis

The vulnerability, identified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), exists in the core functionality of Citrix NetScaler ADC and Gateway. Exploitation of this flaw can lead to a denial of service condition on the affected appliance. Specific details regarding the exploit mechanism or the exact memory operation leading to the DoS are not publicly detailed beyond the CWE classification.

Affected versions include:
* Citrix NetScaler ADC:
* All versions before 14.1-73.41
* All versions before 13.1-64.28
* All FIPS versions before 14.1-73.41
* All versions before 13.1-37.282
* Citrix NetScaler Gateway:
* All versions before 14.1-73.41
* All versions before 13.1-64.28

The attack vector is not explicitly detailed but typically involves sending specially crafted network requests to the vulnerable appliance. Prerequisites for exploitation are not publicly known, but likely involve network accessibility to the NetScaler instance.

Detection

Detecting exploitation of CVE-2026-88779 primarily relies on monitoring the health and availability of Citrix NetScaler appliances.
* Appliance Health Monitoring: Monitor NetScaler appliance uptime, CPU utilization, memory usage, and network throughput for abnormal spikes or sustained high levels indicative of a DoS attack.
* System Logs: Review NetScaler system logs for unexpected restarts, crash reports, or error messages related to memory management or service instability. Specific log patterns for this vulnerability are not publicly detailed.
* Network Traffic Analysis: Look for unusual patterns in network traffic directed at NetScaler appliances, such as high volumes of specific request types or malformed packets, though specific signatures are not available.

Due to the nature of a DoS vulnerability on a network appliance and the lack of specific exploit details or unique log events, generic SIEM rules for this specific CVE are difficult to formulate without vendor-specific telemetry or more granular exploit information.

Mitigations

  1. Apply Patches: Immediately upgrade Citrix NetScaler ADC and Gateway instances to the patched versions.
    • ADC: 14.1-73.41 or later, 13.1-64.28 or later, 14.1-73.41 FIPS or later, 13.1-37.282 or later.
    • Gateway: 14.1-73.41 or later, 13.1-64.28 or later.
  2. Network Segmentation: Restrict network access to NetScaler management interfaces and critical services to only trusted sources and necessary administrative subnets.
  3. Rate Limiting: Implement rate limiting on public-facing NetScaler virtual servers to mitigate high-volume DoS attempts.
  4. Regular Monitoring: Continuously monitor appliance health and performance metrics to detect and respond to potential DoS conditions promptly.

References

  • https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX697174
  • https://community.citrix.com/techzone-blogs/110_security-updates/understanding-and-addressing-cve-2026-88779-in-citrix-netscaler-adc-and-citrix-netscaler-gateway/
  • https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-88779

Indicators of Compromise

No public IOCs available at time of writing.

🤖 AI Attribution
Generated by gemini-2.5-flash ·
1,800 input / 1,185 output tokens ·
Reviewed and approved by a human analyst before publication
Posted in vulnerabilityTagged citrix, denial-of-service, high, kev, netscaler, vulnerabilityLeave a comment
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