CyberSecBulletin
CVE-2024-20450NVD status: Analyzed

Cisco Small Business IP Phones: Buffer Copy without Checking Size of Input

Published Updated By the CyberSecBulletin desk

CVE-2024-20450 is a critical-severity buffer copy without checking size of input vulnerability in Cisco Small Business IP Phones from Cisco, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Cisco Small Business IP Phones versions: 7.6.0; 7.6.2; 7.6.2SR3, 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 7.22% chance of exploitation within 30 days, which is in the top 5.58% of all scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Check which version of Cisco Small Business IP Phones you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on sec.cloudapps.cisco.com for workarounds and exact fixed builds.
  3. 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
CiscoCisco Small Business IP Phones7.6.0; 7.6.2; 7.6.2SR3; 7.6.2SR6; 7.6.2SR2; 7.6.2SR4; 7.6.2SR1; 7.6.2SR5; and 25 more rangesNot stated
Ciscosmall_business_ip_phone_firmware7.6.0; 7.6.2; 7.6.2sr3; 7.6.2sr6; 7.6.2sr2; 7.6.2sr4; 7.6.2sr1; 7.6.2sr5; and 24 more rangesNot stated
CiscoSpa 301 FirmwareNot specified in the recordNot stated
CiscoSpa 303 FirmwareNot specified in the recordNot stated
CiscoSpa 501g FirmwareNot specified in the recordNot stated
CiscoSpa 502g FirmwareNot specified in the recordNot stated
CiscoSpa 504g FirmwareNot specified in the recordNot stated
CiscoSpa 508g FirmwareNot specified in the recordNot stated
CiscoSpa 509g FirmwareNot specified in the recordNot stated
CiscoSpa 512g FirmwareNot specified in the recordNot stated
CiscoSpa 514g FirmwareNot specified in the recordNot stated
CiscoSpa 525g FirmwareNot specified in the recordNot stated
CiscoSpa 525g2 FirmwareNot specified in the recordNot stated

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
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
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:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.19.8CriticalCNA (cisco.com)
CVSS 3.19.8CriticalNVD

Official description

Multiple vulnerabilities in the web-based management interface of Cisco Small Business SPA300 Series IP Phones and Cisco Small Business SPA500 Series IP Phones could allow an unauthenticated, remote attacker to execute arbitrary commands on the underlying operating system with root privileges. These vulnerabilities exist because incoming HTTP packets are not properly checked for errors, which could result in a buffer overflow. An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected device. A successful exploit could allow the attacker to overflow an internal buffer and execute arbitrary commands at the root privilege level.

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

The underlying weakness: Buffer Copy without Checking Size of Input

The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • 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 Buffer Copy without Checking Size of Input vulnerabilities (CWE-120)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Cisco Small Business IP Phones

All Cisco Small Business IP Phones vulnerabilities

Recent Buffer Copy without Checking Size of Input vulnerabilities

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