Security Resilience

CVE-2023-20049

Memory Safety in Cisco Ios Xr ≤ 7.5.3

Memory Safety
Published
09 March 2023
Modified
21 November 2024
Patch / advisory
View advisory
CVSS Score v3.1 8.6
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
EPSS Score 0.010 64th percentile
Risk Priority 64 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2023-20049 is a high-severity Buffer Access with Incorrect Length Value (CWE-805) vulnerability in Cisco Ios Xr. Its CVSS base score is 8.6 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Data Obfuscation (T1001); ranked in the top 36% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability Data

A vulnerability in the bidirectional forwarding detection (BFD) hardware offload feature of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers, ASR 9902 Compact High-Performance Routers, and ASR 9903 Compact High-Performance Routers could allow an unauthenticated, remote…

more

attacker to cause a line card to reset, resulting in a denial of service (DoS) condition. This vulnerability is due to the incorrect handling of malformed BFD packets that are received on line cards where the BFD hardware offload feature is enabled. An attacker could exploit this vulnerability by sending a crafted IPv4 BFD packet to an affected device. A successful exploit could allow the attacker to cause line card exceptions or a hard reset, resulting in loss of traffic over that line card while the line card reloads.

CWE(s)
CWE-805CWE-119

Related Threats

MITRE ATT&CK Enterprise Techniques

T1001 Data Obfuscation Command And Control
Adversaries may obfuscate command and control traffic to make it more difficult to detect.
attack.mitre.org →
T1003.001 LSASS Memory Credential Access
Adversaries may attempt to access credential material stored in the process memory of the Local Security Authority Subsystem Service (LSASS).
attack.mitre.org →
T1003.005 Cached Domain Credentials Credential Access
Adversaries may attempt to access cached domain credentials used to allow authentication to occur in the event a domain controller is unavailable.
attack.mitre.org →
T1003.006 DCSync Credential Access
Adversaries may attempt to access credentials and other sensitive information by abusing a Windows Domain Controller's application programming interface (API)(Citation: Microsoft DRSR Dec 2017) (Citation: Microsoft GetNCCChanges) (Citati…
attack.mitre.org →
T1008 Fallback Channels Command And Control
Adversaries may use fallback or alternate communication channels if the primary channel is compromised or inaccessible in order to maintain reliable command and control and to avoid data transfer thresholds.
attack.mitre.org →
T1012 Query Registry Discovery
Adversaries may interact with the Windows Registry to gather information about the system, configuration, and installed software.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-20327Same product: Cisco Asr 9000V-V2
CVE-2025-20142Same product: Cisco Asr 9006
CVE-2025-20146Same product: Cisco Asr 9006
CVE-2020-3566Same product: Cisco Asr 9001
CVE-2025-20174Same vendor: Cisco
CVE-2025-20170Same vendor: Cisco
CVE-2025-20169Same vendor: Cisco
CVE-2025-20315Same vendor: Cisco
CVE-2024-20294Same vendor: Cisco
CVE-2025-20202Same vendor: Cisco

Affected Assets

cisco
ios xr
7.7 · ≤ 7.5.3 · 7.6 — 7.6.2

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.4.1

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SA-11 Developer Testing and Evaluation
addresses: CWE-119

Ongoing control assessments and code testing (static/dynamic analysis, fuzzing) surface memory buffer restriction failures, which are then remediated before release.

SC-27 Platform-independent Applications
addresses: CWE-119

Managed runtimes used by platform-independent applications (e.g., JVM, CLR) enforce memory safety, preventing most buffer overflows that require direct memory manipulation.

SI-16 Memory Protection
addresses: CWE-119

Memory protections (e.g., W^X, ASLR) make exploitation of buffer-boundary violations far harder to turn into code execution.

SI-4 System Monitoring
addresses: CWE-119

Detects exploitation attempts that produce memory corruption, crashes, or anomalous behavior.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

ID.RA-01 partial match
blocks

Vulnerability identification can discover buffer-length flaws but does not prevent their introduction.

PR.PS-06 partial match
blocks

Secure SDLC practices directly prevent incorrect-length buffer operations via safe APIs, reviews, and testing.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.6.4 Disciplinary process partial match
removes
A.8.2 Privileged access rights partial match
removes
A.8.25 Secure development life cycle partial match
blocks

A.8.25 mandates secure SDLC practices including secure coding guidelines, security requirements, checkpoints, testing (scans/penetration), and developer training that reach buffer-length issues in custom code, but leaves a bounded remainder (e.g. third-party libraries, legacy code, incomplete enforcement of guidelines, or outsourced development without full assurance).

A.8.26 Application security requirements partial match
blocks

Application security requirements can specify buffer-size validation, but do not prescribe implementation details.

A.8.27 Secure system architecture and engineering principles partial match
blocks

A.8.27 mandates security-by-design, defence-in-depth, least privilege, distrust-external-input, hardening, and design reviews against known attack patterns; these reach a minority slice of CWE-805 (e.g. safe API selection or bounds-aware length computation) but leave most buffer-length errors still introducible and exploitable in the remaining implementation surface.

A.8.28 Secure coding partial match
prevents

Secure coding explicitly requires correct buffer-length handling, eliminating CWE-805 when followed.

Hardening callouts derived

DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.

  • No fine-grained STIG row for CWE-119, a class-level weakness. Rules are authored against its narrower children: CWE-823.

References