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🛡️ CVE-2026-20039 — adaptive-security-appliance-software

🟠 CVSS 8.6 — High ✅ No Known Exploit CWE-244 NVD
8.6
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

A vulnerability in the VPN web server 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 a denial of service (DoS) condition on an affected device.

This vulnerability is due to ineffective memory management of the VPN web server. An attacker could exploit this vulnerability by sending a large number of crafted HTTP requests to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Changed — a successful attack reaches components beyond the vulnerable one.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-20039 is classified as CWE-244: Improper Clearing of Heap Memory Before Release ('Heap Inspection'). Using realloc() to resize buffers that store sensitive information can leave the sensitive information exposed to attack, because it is not removed from memory.

Affected software

CVE-2026-20039 is recorded against 2 packages.

  • adaptive-security-appliance-software (from 9.23.1 up to 9.23.1.3)
  • secure-firewall-threat-defense (from 7.7.0 up to 7.7.10)

Timeline and source

Published on 4 March 2026 and last revised on 11 August 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

sec.cloudapps.cisco.com

Other advisories for this package

adaptive-security-appliance-software has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-244: Improper Clearing of Heap Memory Before Release ('Heap Inspection')) in other software:

Details

Severity HIGH
CVSS Score 8.6
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CWE CWE-244
Public Exploit ✅ No
Source NVD
Published 2026-03-04
Updated 2026-08-20
Modified 2026-08-11
Fix URL N/A

Affected Packages

Software From version Fixed in
adaptive-security-appliance-software 9.23.1 9.23.1.3
secure-firewall-threat-defense 7.7.0 7.7.10

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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