CVE-2023-20233Network attack vector

CFM service crash via invalid CCM processing

Published Sep 13, 2023 · Updated Aug 2, 2024

Denial of service in Cisco IOS XR Software allows remote attackers to crash the CFM service by sending crafted continuity check messages. The CFM message-processing path incorrectly processes invalid CCMs, and Cisco maps the flaw to a NULL pointer dereference. Exploitation requires CFM, which is disabled by default, receipt of a crafted CCM, and a user displaying peer MEP information; the resulting crash interrupts the CFM service.

CVSS severity4.3
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco IOS XR Software allows remote attackers to crash the CFM service by sending crafted continuity check messages. The CFM message-processing path incorrectly processes invalid CCMs, and Cisco maps the flaw to a NULL pointer dereference. Exploitation requires CFM, which is disabled by default, receipt of a crafted CCM, and a user displaying peer MEP information; the resulting crash interrupts the CFM service.

The record

CVE
CVE-2023-20233
Published
Sep 13, 2023
Updated
Aug 2, 2024
Vendor
ClamAV
Product
Cisco IOS XR Software
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 13, 2023CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.2.0
  2. Affected versionversion=5.2.1
  3. Affected versionversion=5.2.2
  4. Affected versionversion=5.2.3
  5. Affected versionversion=5.2.4
  6. Affected versionversion=5.2.5
  7. Affected versionversion=5.3.0
  8. Affected versionversion=5.3.1
  9. Affected versionversion=5.3.2
  10. Affected versionversion=5.3.3
  11. Affected versionversion=5.3.4
  12. Affected versionversion=6.1.1
  13. Affected versionversion=6.1.2
  14. Affected versionversion=6.1.3
  15. Affected versionversion=6.1.4
  16. Affected versionversion=6.2.1
  17. Affected versionversion=6.2.2
  18. Affected versionversion=6.2.25
  19. Affected versionversion=6.2.3
  20. Affected versionversion=6.3.15
  21. Affected versionversion=6.3.2
  22. Affected versionversion=6.3.3
  23. Affected versionversion=6.4.1
  24. Affected versionversion=6.4.2
  25. Affected versionversion=6.4.3
  26. Affected versionversion=6.5.1
  27. Affected versionversion=6.5.2
  28. Affected versionversion=6.6.2
  29. Affected versionversion=6.6.25
  30. Affected versionversion=6.6.3
  31. Affected versionversion=6.6.4
  32. Affected versionversion=6.7.1
  33. Affected versionversion=6.7.2
  34. Affected versionversion=6.7.3
  35. Affected versionversion=6.7.4
  36. Affected versionversion=6.8.1
  37. Affected versionversion=6.8.2
  38. Affected versionversion=6.9.1
  39. Affected versionversion=6.9.2
  40. Affected versionversion=7.0.1
  41. Affected versionversion=7.0.2
  42. Affected versionversion=7.1.1
  43. Affected versionversion=7.1.15
  44. Affected versionversion=7.1.2
  45. Affected versionversion=7.1.3
  46. Affected versionversion=7.2.1
  47. Affected versionversion=7.2.2
  48. Affected versionversion=7.3.1
  49. Affected versionversion=7.3.2
  50. Affected versionversion=7.3.3
  51. Affected versionversion=7.4.1
  52. Affected versionversion=7.4.2
  53. Affected versionversion=7.5.1
  54. Affected versionversion=7.5.2
  55. Affected versionversion=7.5.3
  56. Affected versionversion=7.6.1
  57. Affected versionversion=7.6.2
  58. Affected versionversion=7.7.1
  59. Affected versionversion=7.7.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco IOS XR Softwareversion=5.2.0; version=5.2.1; version=5.2.2; version=5.2.3; version=5.2.4; version=5.2.5; version=5.3.0; version=5.3.1; version=5.3.2; version=5.3.3; version=5.3.4; version=6.1.1; version=6.1.2; version=6.1.3; version=6.1.4; version=6.2.1; version=6.2.2; version=6.2.25; version=6.2.3; version=6.3.15; version=6.3.2; version=6.3.3; version=6.4.1; version=6.4.2; version=6.4.3; version=6.5.1; version=6.5.2; version=6.6.2; version=6.6.25; version=6.6.3; version=6.6.4; version=6.7.1; version=6.7.2; version=6.7.3; version=6.7.4; version=6.8.1; version=6.8.2; version=6.9.1; version=6.9.2; version=7.0.1; version=7.0.2; version=7.1.1; version=7.1.15; version=7.1.2; version=7.1.3; version=7.2.1; version=7.2.2; version=7.3.1; version=7.3.2; version=7.3.3; version=7.4.1; version=7.4.2; version=7.5.1; version=7.5.2; version=7.5.3; version=7.6.1; version=7.6.2; version=7.7.1; version=7.7.2

Published CVSS scores

4.3CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L/E:X/RL:X/RC:X

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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