CyberSecBulletin
CVE-2025-20363NVD status: Analyzed

IOS: Heap-based Buffer Overflow

Published Updated By the CyberSecBulletin desk

CVE-2025-20363 is a critical-severity heap-based buffer overflow vulnerability in IOS from Cisco, with a CVSS 3.1 base score of 9.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected IOS versions: 12.2(15)B; 12.2(16)B1; 12.2(16)B2, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 7.16% chance of exploitation within 30 days, which is in the top 5.62% of all scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Adaptive Security Appliance Software to 9.12.4.72 or 9.14.4.28 or 9.16.4.84 or 9.18.4.57, whichever matches your release line, or a later version.
  2. Update Secure Firewall Threat Defense to 7.0.8 or 7.2.10 or 7.4.2.3 or 7.7.10, whichever matches your release line, or a later version.
  3. Read the advisory on sec.cloudapps.cisco.com for workarounds and exact fixed builds.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
CiscoIOS12.2(15)B; 12.2(16)B1; 12.2(16)B2; 12.2(16)B; 12.2(15)BC2a; 12.2(15)BC1a; 12.2(15)BC1b; 12.2(15)BC2d; and 32 more rangesNot stated
CiscoCisco IOS XR Software6.5.1; 6.5.2; 6.5.3; 6.6.2; 6.6.3; 6.6.25; 6.7.1; 6.7.2; and 5 more rangesNot stated
CiscoCisco Adaptive Security Appliance (ASA) Software9.8.1; 9.8.1.5; 9.8.1.7; 9.8.2; 9.8.2.8; 9.8.2.14; 9.8.2.15; 9.8.2.17; and 32 more rangesNot stated
CiscoCisco IOS XE Software3.2.0SG; 3.2.1SG; 3.2.2SG; 3.2.3SG; 3.2.4SG; 3.2.5SG; 3.2.6SG; 3.2.7SG; and 32 more rangesNot stated
CiscoCisco Firepower Threat Defense Software6.2.3; 6.2.3.1; 6.2.3.2; 6.2.3.3; 6.2.3.4; 6.2.3.5; 6.2.3.6; 6.2.3.7; and 32 more rangesNot stated
CiscoiOS Xr6.5.1; 6.5.2; 6.5.3; 6.6.2; 6.6.3; 6.6.25; 6.7.1; 6.7.2; and 5 more rangesNot stated
CiscoAdaptive Security Appliance Software9.12 up to, but not including, 9.12.4.72; 9.14 up to, but not including, 9.14.4.28; 9.16 up to, but not including, 9.16.4.84; 9.17.1 up to, but not including, 9.18.4.57; 9.19.1 up to, but not including, 9.19.1.42; 9.20.1 up to, but not including, 9.20.3.16; 9.22 up to, but not including, 9.22.2; 9.23 up to, but not including, 9.23.1.39.12.4.72, 9.14.4.28, 9.16.4.84, 9.18.4.57, 9.19.1.42, 9.20.3.16
CiscoiOS Xe3.2.0sg through 17.17.1Not stated
CiscoSecure Firewall Threat Defense7.0.0 up to, but not including, 7.0.8; 7.1.0 up to, but not including, 7.2.10; 7.3.0 up to, but not including, 7.4.2.3; 7.7.0 up to, but not including, 7.7.10; 7.6.07.0.8, 7.2.10, 7.4.2.3, 7.7.10

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
HighSuccess depends on conditions outside the attacker's control.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (cisco.com).

Official description

A vulnerability in the web services of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Secure Firewall Threat Defense (FTD) Software, Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software could allow an unauthenticated, remote attacker (Cisco ASA and FTD Software) or authenticated, remote attacker (Cisco IOS, IOS XE, and IOS XR Software) with low user privileges to execute arbitrary code on an affected device. This vulnerability is due to improper validation of user-supplied input in HTTP requests. An attacker could exploit this vulnerability by sending crafted HTTP requests to a targeted web service on an affected device after obtaining additional information about the system, overcoming exploit mitigations, or both. A successful exploit could allow the attacker to execute arbitrary code as root, which may lead to the complete compromise of the affected device. For more information about this vulnerability, see the Details ["#details"] section of this advisory.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Heap-based Buffer Overflow

The product writes past the end of a buffer that was allocated on the heap.

How developers prevent this class of flaw

  • Pre-design: Use a language or compiler that performs automatic bounds checking.
  • Use an abstraction library to abstract away risky APIs. Not a complete solution.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Heap-based Buffer Overflow vulnerabilities (CWE-122)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in IOS

All IOS vulnerabilities

Recent Heap-based Buffer Overflow vulnerabilities

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