Description

As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco IOS XR Software engineering team has conducted a comprehensive internal security review. This review resulted in a software hardening releases that address multiple internally discovered vulnerabilities. The vulnerabilities tracked by CVE-2026-20275 are related to incorrect calculation issues that are grouped under the Common Weakness Enumeration (CWE) CWE-682.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-02T17:17:32.790Z",
  "pubdate": "2026-09-02T17:17:32.790Z",
  "executiveSummary": "Cisco IOS XR Software contains multiple vulnerabilities classified under CWE-682 (Incorrect Calculation).\nThese vulnerabilities, tracked under CVE-2026-20275, originate from internal security reviews conducted by Cisco's engineering team.\nThe flaws pertain to logic errors in data processing calculations within the software.\nExploitation of these calculation inaccuracies could potentially lead to inconsistent system states, improper resource management, or denial of service conditions, depending on the specific context of the calculation.\nThe scope of impact is limited to the affected Cisco IOS XR software ecosystem.\nThese issues do not require external researcher discovery, as they were identified during proactive internal hardening efforts.",
  "technicalDetails": "The vulnerabilities identified as CVE-2026-20275 are rooted in the logical handling of arithmetic or algorithmic operations within the Cisco IOS XR Software codebase, conforming to the CWE-682 classification of Incorrect Calculation.\nAt the architectural level, these flaws manifest when software components perform mathematical operations on input data, configuration parameters, or packet metadata that result in unintended numerical outcomes. Incorrect calculations often stem from improper handling of integer overflows, sign mismatches, precision loss, or incorrect logic branches based on calculated values.\nThe attack flow for such vulnerabilities generally involves an attacker injecting specifically crafted inputs—either through management interfaces, network protocol headers, or malformed configuration files—that trigger the vulnerable calculation path.\nBecause the vulnerability lies in the core logic of the IOS XR software, once the malformed input reaches the vulnerable function, the system processes the incorrect result. This can lead to various outcomes: memory corruption if the result is used to calculate buffer offsets; privilege escalation if the result dictates authorization logic; or system instability if the calculation is critical to the operating system's kernel tasks or process scheduling.\nThe impact is strictly tied to the specific software module utilizing the erroneous logic. If the calculation pertains to packet length, an attacker might leverage this to trigger heap or stack overflows via off-by-one errors. If the calculation involves internal resource allocation, an attacker could force exhaustion of memory or processing cycles, leading to a service disruption.\nDue to the nature of internally discovered flaws in Cisco IOS XR, these vulnerabilities are likely embedded in fundamental system libraries or kernel-level components. Successful exploitation usually necessitates a degree of interaction with the system's control plane or data plane, depending on where the calculation is performed. As this was discovered during a hardening cycle, the remediation requires precise refactoring of the mathematical logic to ensure that all edge cases, input bounds, and data type constraints are rigorously validated before the calculation completes."
}