CVE-2026-20281Network attack vector

Persistent service outage via HTTP memory exhaustion

Published Sep 2, 2026 · Updated Sep 2, 2026

Memory exhaustion in Cisco SIP IP Phone Software allows remote attackers to force an affected phone into a persistent service outage. The HTTP packet-processing path improperly manages memory while handling a continuous stream of crafted packets, causing consumption to grow until service fails. The phone must be registered to Unified CM with default-disabled Web Access enabled, and recovery requires a manual reboot.

CVSS severity7.5
High
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory exhaustion in Cisco SIP IP Phone Software allows remote attackers to force an affected phone into a persistent service outage. The HTTP packet-processing path improperly manages memory while handling a continuous stream of crafted packets, causing consumption to grow until service fails. The phone must be registered to Unified CM with default-disabled Web Access enabled, and recovery requires a manual reboot.

The record

CVE
CVE-2026-20281
Published
Sep 2, 2026
Updated
Sep 2, 2026
Vendor
ClamAV
Product
Cisco SIP IP Phone Software
Classifications
CWE-401, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=10.1(1.9)
  2. Affected versionversion=10.1(1)SR1
  3. Affected versionversion=10.1(1)SR2
  4. Affected versionversion=10.2(1)
  5. Affected versionversion=10.2(1)SR1
  6. Affected versionversion=10.2(2)
  7. Affected versionversion=10.3(1)
  8. Affected versionversion=10.3(1.11) 3rd Party
  9. Affected versionversion=10.3(1.9) 3rd Party
  10. Affected versionversion=10.3(1)SR1
  11. Affected versionversion=10.3(1)SR2
  12. Affected versionversion=10.3(1)SR3
  13. Affected versionversion=10.3(1)SR4
  14. Affected versionversion=10.3(1)SR4b
  15. Affected versionversion=10.3(1)SR5
  16. Affected versionversion=10.3(1)SR6
  17. Affected versionversion=10.3(1)SR7
  18. Affected versionversion=10.3(2)
  19. Affected versionversion=10.4(1) 3rd Party
  20. Affected versionversion=10.4(1)SR2 3rd Party
  21. Affected versionversion=11.0(0.7) MPP
  22. Affected versionversion=11.0(1)
  23. Affected versionversion=11-0-1MSR1-1
  24. Affected versionversion=11.0(2)
  25. Affected versionversion=11.0(2)SR1
  26. Affected versionversion=11.0(2)SR2
  27. Affected versionversion=11.0(3)
  28. Affected versionversion=11.0(3)SR1
  29. Affected versionversion=11.0(3)SR2
  30. Affected versionversion=11.0(3)SR3
  31. Affected versionversion=11.0(3)SR4
  32. Affected versionversion=11.0(3)SR5
  33. Affected versionversion=11.0(3)SR6
  34. Affected versionversion=11.0(4)
  35. Affected versionversion=11.0(4)SR1
  36. Affected versionversion=11.0(4)SR2
  37. Affected versionversion=11.0(4)SR3
  38. Affected versionversion=11.0(5)
  39. Affected versionversion=11.0(5)SR1
  40. Affected versionversion=11.0(5)SR2
  41. Affected versionversion=11.0(5)SR3
  42. Affected versionversion=11.0(6)
  43. Affected versionversion=11.0(6)SR1
  44. Affected versionversion=11.0(6)SR2
  45. Affected versionversion=11.0(6)SR4
  46. Affected versionversion=11.0(6)SR5
  47. Affected versionversion=11.0(6)SR6
  48. Affected versionversion=11.0(6)SR7
  49. Affected versionversion=11.5(1)
  50. Affected versionversion=11.5(1)SR1
  51. Affected versionversion=11.7(1)
  52. Affected versionversion=12.0(1)
  53. Affected versionversion=12.0(1)SR1
  54. Affected versionversion=12.0(1)SR2
  55. Affected versionversion=12.0(1)SR3
  56. Affected versionversion=12.1(1)
  57. Affected versionversion=12.1(1)SR1
  58. Affected versionversion=12.5(1)
  59. Affected versionversion=12.5(1)SR1
  60. Affected versionversion=12.5(1)SR2
  61. Affected versionversion=12.5(1)SR3
  62. Affected versionversion=12.6(1)
  63. Affected versionversion=12.6(1)SR1
  64. Affected versionversion=12.7(1)
  65. Affected versionversion=12.7(1)SR1
  66. Affected versionversion=12.8(1)
  67. Affected versionversion=12.8(1)SR1
  68. Affected versionversion=12.8(1)SR2
  69. Affected versionversion=14.0(1)
  70. Affected versionversion=14.0(1)SR1
  71. Affected versionversion=14.0(1)SR2
  72. Affected versionversion=14.0(1)SR3
  73. Affected versionversion=14.1(1)
  74. Affected versionversion=14.1(1)SR1
  75. Affected versionversion=14.1(1)SR2
  76. Affected versionversion=14.1(1)SR3
  77. Affected versionversion=14.2(1)
  78. Affected versionversion=14.2(1)SR1
  79. Affected versionversion=14.2(1)SR2
  80. Affected versionversion=14.2(1)SR3
  81. Affected versionversion=14.2(1)SR4
  82. Affected versionversion=14.3(1)
  83. Affected versionversion=14.3(1)SR1
  84. Affected versionversion=14.3(1)SR2
  85. Affected versionversion=14.3(1)SR3
  86. Affected versionversion=14.4(1)
  87. Affected versionversion=14.4(1)SR1
  88. Affected versionversion=14.4(1)SR2
  89. Affected versionversion=2.0(1)
  90. Affected versionversion=2.1(1)
  91. Affected versionversion=2.2(1)
  92. Affected versionversion=2.3(1)
  93. Affected versionversion=2.3(1)SR1
  94. Affected versionversion=3.0(1)
  95. Affected versionversion=3.1(1)
  96. Affected versionversion=3.1(1)SR1
  97. Affected versionversion=3.2(1)
  98. Affected versionversion=3.3(1)
  99. Affected versionversion=3.4(1)
  100. Affected versionversion=3.5(1)
  101. Affected versionversion=3.5(1)SR1
  102. Affected versionversion=3.6(1)
  103. Affected versionversion=4.0(1)
  104. Affected versionversion=4.1(1)
  105. Affected versionversion=4.1(1)SR1
  106. Affected versionversion=9.3(3)
  107. Affected versionversion=9.3(4) 3rd Party
  108. Affected versionversion=9.3(4)SR1 3rd Party
  109. Affected versionversion=9.3(4)SR2 3rd Party
  110. Affected versionversion=9.3(4)SR3 3rd Party

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco SIP IP Phone Softwareversion=10.1(1.9); version=10.1(1)SR1; version=10.1(1)SR2; version=10.2(1); version=10.2(1)SR1; version=10.2(2); version=10.3(1); version=10.3(1.11) 3rd Party; version=10.3(1.9) 3rd Party; version=10.3(1)SR1; version=10.3(1)SR2; version=10.3(1)SR3; version=10.3(1)SR4; version=10.3(1)SR4b; version=10.3(1)SR5; version=10.3(1)SR6; version=10.3(1)SR7; version=10.3(2); version=10.4(1) 3rd Party; version=10.4(1)SR2 3rd Party; version=11.0(0.7) MPP; version=11.0(1); version=11-0-1MSR1-1; version=11.0(2); version=11.0(2)SR1; version=11.0(2)SR2; version=11.0(3); version=11.0(3)SR1; version=11.0(3)SR2; version=11.0(3)SR3; version=11.0(3)SR4; version=11.0(3)SR5; version=11.0(3)SR6; version=11.0(4); version=11.0(4)SR1; version=11.0(4)SR2; version=11.0(4)SR3; version=11.0(5); version=11.0(5)SR1; version=11.0(5)SR2; version=11.0(5)SR3; version=11.0(6); version=11.0(6)SR1; version=11.0(6)SR2; version=11.0(6)SR4; version=11.0(6)SR5; version=11.0(6)SR6; version=11.0(6)SR7; version=11.5(1); version=11.5(1)SR1; version=11.7(1); version=12.0(1); version=12.0(1)SR1; version=12.0(1)SR2; version=12.0(1)SR3; version=12.1(1); version=12.1(1)SR1; version=12.5(1); version=12.5(1)SR1; version=12.5(1)SR2; version=12.5(1)SR3; version=12.6(1); version=12.6(1)SR1; version=12.7(1); version=12.7(1)SR1; version=12.8(1); version=12.8(1)SR1; version=12.8(1)SR2; version=14.0(1); version=14.0(1)SR1; version=14.0(1)SR2; version=14.0(1)SR3; version=14.1(1); version=14.1(1)SR1; version=14.1(1)SR2; version=14.1(1)SR3; version=14.2(1); version=14.2(1)SR1; version=14.2(1)SR2; version=14.2(1)SR3; version=14.2(1)SR4; version=14.3(1); version=14.3(1)SR1; version=14.3(1)SR2; version=14.3(1)SR3; version=14.4(1); version=14.4(1)SR1; version=14.4(1)SR2; version=2.0(1); version=2.1(1); version=2.2(1); version=2.3(1); version=2.3(1)SR1; version=3.0(1); version=3.1(1); version=3.1(1)SR1; version=3.2(1); version=3.3(1); version=3.4(1); version=3.5(1); version=3.5(1)SR1; version=3.6(1); version=4.0(1); version=4.1(1); version=4.1(1)SR1; version=9.3(3); version=9.3(4) 3rd Party; version=9.3(4)SR1 3rd Party; version=9.3(4)SR2 3rd Party; version=9.3(4)SR3 3rd Party

Published CVSS scores

7.5Cisco PSIRTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/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-401Missing Release of Memory after Effective Lifetime
T1499.003Application Exhaustion Flood

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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