Cisco IP Phones with Multiplatform Firmware: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
CVE-2022-20817 is a high-severity use of cryptographically weak pseudo-random number generator (PRNG) vulnerability in Cisco IP Phones with Multiplatform Firmware from Cisco, with a CVSS 3.1 base score of 7.4 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. There is no confirmed exploitation so far. EPSS estimates a 1.23% chance of exploitation within 30 days, higher than 69% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Cisco IP Phones with Multiplatform Firmware you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on tools.cisco.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | Cisco IP Phones with Multiplatform Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 6911 Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 6921 Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 6941 Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 6945 Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 6961 Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 8941 Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 8945 Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 8961 Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 9951 Firmware | Not specified in the record | Not stated |
| Cisco | Unified IP Phone 9971 Firmware | Not specified in the record | Not stated |
| Cisco | Ata 187 Analog Telephone Adapter Firmware | Not specified in the record | Not 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
- 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
- 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
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.4 | High | CNA (cisco.com) |
| CVSS 3.1 | 7.4 | High | NVD |
| CVSS 2.0 | 4.0 | Medium | NVD |
Official description
A vulnerability in Cisco Unified IP Phones could allow an unauthenticated, remote attacker to impersonate another user's phone if the Cisco Unified Communications Manager (CUCM) is in secure mode. This vulnerability is due to improper key generation during the manufacturing process that could result in duplicated manufactured keys installed on multiple devices. An attacker could exploit this vulnerability by performing a machine-in-the-middle attack on the secure communication between the phone and the CUCM. A successful exploit could allow the attacker to impersonate another user's phone. This vulnerability cannot be addressed with software updates. There is a workaround that addresses this vulnerability.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.
How developers prevent this class of flaw
- Use functions or hardware which use a hardware-based random number generation for all crypto. This is the recommended solution. Use CyptGenRandom on Windows, or hw_rand() on Linux.
More Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) vulnerabilities (CWE-338)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in Cisco IP Phones with Multiplatform Firmware
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
Recent Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) vulnerabilities
- 7.5 High severity
- 7.5 High severity
Spotted an error? Tell us.