Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service
CVE-2009-2055 is a medium-severity improper input validation vulnerability in iOS Xr from Cisco, with a CVSS 2.0 base score of 4.3 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected iOS Xr versions: 3.4; 3.4.0; 3.4.1, and others listed below. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on March 25, 2022, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Check which version of iOS Xr you run against the affected versions below, and install the vendor's latest release.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on 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 | iOS Xr | 3.4; 3.4.0; 3.4.1; 3.4.2; 3.4.3; 3.5; 3.5.2; 3.5.3; and 11 more ranges | Not stated |
Version data comes from NVD's product matching. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Access vector
- NetworkCan be exploited remotely over a network.
- Access complexity
- MediumSome conditions must be met.
- Authentication
- NoneNo login is needed.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- PartialAvailability is reduced.
Vector: AV:N/AC:M/Au:N/C:N/I:N/A:P. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 5.9 | Medium | CISA (ADP) |
| CVSS 2.0 | 4.3 | Medium | NVD |
Official description
Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an invalid attribute, as demonstrated in the wild on 17 August 2009.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Input Validation
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
How developers prevent this class of flaw
- Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
- Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
- Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2009-2055US Government Resource
Other references
Other vulnerabilities in iOS Xr
- 8.8 High severity
- 8.6 High severity
- 9.8 Critical severity
- 7.4 High severity
- 8.8 High severity
- 8.8 High severity
Recent Improper Input Validation vulnerabilities
- 8.8 High severity
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