CVE-2026-5545Network attack vector

Authentication bypass via Negotiate connection reuse

Published May 13, 2026 · Updated May 13, 2026

Authentication bypass in curl 7.10.6 through 8.19.0 allows remote attackers to send requests under prior Negotiate credentials. The url_match_auth_ntlm function in lib/url.c accepts a credential-mismatched pooled connection when NTLM is idle without also rejecting an active Negotiate state. Reachability requires a live connection to the same host that first used Negotiate credentials and a later request using different credentials; that request runs with the first identity.

CVSS severity6.5
Medium
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in curl 7.10.6 through 8.19.0 allows remote attackers to send requests under prior Negotiate credentials. The url_match_auth_ntlm function in lib/url.c accepts a credential-mismatched pooled connection when NTLM is idle without also rejecting an active Negotiate state. Reachability requires a live connection to the same host that first used Negotiate credentials and a later request using different credentials; that request runs with the first identity.

The record

CVE
CVE-2026-5545
Published
May 13, 2026
Updated
May 13, 2026
Vendor
curl
Product
curl
Classifications
CWE-613, CWE-305, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 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=7.10.6 <=7.10.6
  2. Affected versionversion=7.10.7 <=7.10.7
  3. Affected versionversion=7.10.8 <=7.10.8
  4. Affected versionversion=7.11.0 <=7.11.0
  5. Affected versionversion=7.11.1 <=7.11.1
  6. Affected versionversion=7.11.2 <=7.11.2
  7. Affected versionversion=7.12.0 <=7.12.0
  8. Affected versionversion=7.12.1 <=7.12.1
  9. Affected versionversion=7.12.2 <=7.12.2
  10. Affected versionversion=7.12.3 <=7.12.3
  11. Affected versionversion=7.13.0 <=7.13.0
  12. Affected versionversion=7.13.1 <=7.13.1
  13. Affected versionversion=7.13.2 <=7.13.2
  14. Affected versionversion=7.14.0 <=7.14.0
  15. Affected versionversion=7.14.1 <=7.14.1
  16. Affected versionversion=7.15.0 <=7.15.0
  17. Affected versionversion=7.15.1 <=7.15.1
  18. Affected versionversion=7.15.2 <=7.15.2
  19. Affected versionversion=7.15.3 <=7.15.3
  20. Affected versionversion=7.15.4 <=7.15.4
  21. Affected versionversion=7.15.5 <=7.15.5
  22. Affected versionversion=7.16.0 <=7.16.0
  23. Affected versionversion=7.16.1 <=7.16.1
  24. Affected versionversion=7.16.2 <=7.16.2
  25. Affected versionversion=7.16.3 <=7.16.3
  26. Affected versionversion=7.16.4 <=7.16.4
  27. Affected versionversion=7.17.0 <=7.17.0
  28. Affected versionversion=7.17.1 <=7.17.1
  29. Affected versionversion=7.18.0 <=7.18.0
  30. Affected versionversion=7.18.1 <=7.18.1
  31. Affected versionversion=7.18.2 <=7.18.2
  32. Affected versionversion=7.19.0 <=7.19.0
  33. Affected versionversion=7.19.1 <=7.19.1
  34. Affected versionversion=7.19.2 <=7.19.2
  35. Affected versionversion=7.19.3 <=7.19.3
  36. Affected versionversion=7.19.4 <=7.19.4
  37. Affected versionversion=7.19.5 <=7.19.5
  38. Affected versionversion=7.19.6 <=7.19.6
  39. Affected versionversion=7.19.7 <=7.19.7
  40. Affected versionversion=7.20.0 <=7.20.0
  41. Affected versionversion=7.20.1 <=7.20.1
  42. Affected versionversion=7.21.0 <=7.21.0
  43. Affected versionversion=7.21.1 <=7.21.1
  44. Affected versionversion=7.21.2 <=7.21.2
  45. Affected versionversion=7.21.3 <=7.21.3
  46. Affected versionversion=7.21.4 <=7.21.4
  47. Affected versionversion=7.21.5 <=7.21.5
  48. Affected versionversion=7.21.6 <=7.21.6
  49. Affected versionversion=7.21.7 <=7.21.7
  50. Affected versionversion=7.22.0 <=7.22.0
  51. Affected versionversion=7.23.0 <=7.23.0
  52. Affected versionversion=7.23.1 <=7.23.1
  53. Affected versionversion=7.24.0 <=7.24.0
  54. Affected versionversion=7.25.0 <=7.25.0
  55. Affected versionversion=7.26.0 <=7.26.0
  56. Affected versionversion=7.27.0 <=7.27.0
  57. Affected versionversion=7.28.0 <=7.28.0
  58. Affected versionversion=7.28.1 <=7.28.1
  59. Affected versionversion=7.29.0 <=7.29.0
  60. Affected versionversion=7.30.0 <=7.30.0
  61. Affected versionversion=7.31.0 <=7.31.0
  62. Affected versionversion=7.32.0 <=7.32.0
  63. Affected versionversion=7.33.0 <=7.33.0
  64. Affected versionversion=7.34.0 <=7.34.0
  65. Affected versionversion=7.35.0 <=7.35.0
  66. Affected versionversion=7.36.0 <=7.36.0
  67. Affected versionversion=7.37.0 <=7.37.0
  68. Affected versionversion=7.37.1 <=7.37.1
  69. Affected versionversion=7.38.0 <=7.38.0
  70. Affected versionversion=7.39.0 <=7.39.0
  71. Affected versionversion=7.40.0 <=7.40.0
  72. Affected versionversion=7.41.0 <=7.41.0
  73. Affected versionversion=7.42.0 <=7.42.0
  74. Affected versionversion=7.42.1 <=7.42.1
  75. Affected versionversion=7.43.0 <=7.43.0
  76. Affected versionversion=7.44.0 <=7.44.0
  77. Affected versionversion=7.45.0 <=7.45.0
  78. Affected versionversion=7.46.0 <=7.46.0
  79. Affected versionversion=7.47.0 <=7.47.0
  80. Affected versionversion=7.47.1 <=7.47.1
  81. Affected versionversion=7.48.0 <=7.48.0
  82. Affected versionversion=7.49.0 <=7.49.0
  83. Affected versionversion=7.49.1 <=7.49.1
  84. Affected versionversion=7.50.0 <=7.50.0
  85. Affected versionversion=7.50.1 <=7.50.1
  86. Affected versionversion=7.50.2 <=7.50.2
  87. Affected versionversion=7.50.3 <=7.50.3
  88. Affected versionversion=7.51.0 <=7.51.0
  89. Affected versionversion=7.52.0 <=7.52.0
  90. Affected versionversion=7.52.1 <=7.52.1
  91. Affected versionversion=7.53.0 <=7.53.0
  92. Affected versionversion=7.53.1 <=7.53.1
  93. Affected versionversion=7.54.0 <=7.54.0
  94. Affected versionversion=7.54.1 <=7.54.1
  95. Affected versionversion=7.55.0 <=7.55.0
  96. Affected versionversion=7.55.1 <=7.55.1
  97. Affected versionversion=7.56.0 <=7.56.0
  98. Affected versionversion=7.56.1 <=7.56.1
  99. Affected versionversion=7.57.0 <=7.57.0
  100. Affected versionversion=7.58.0 <=7.58.0
  101. Affected versionversion=7.59.0 <=7.59.0
  102. Affected versionversion=7.60.0 <=7.60.0
  103. Affected versionversion=7.61.0 <=7.61.0
  104. Affected versionversion=7.61.1 <=7.61.1
  105. Affected versionversion=7.62.0 <=7.62.0
  106. Affected versionversion=7.63.0 <=7.63.0
  107. Affected versionversion=7.64.0 <=7.64.0
  108. Affected versionversion=7.64.1 <=7.64.1
  109. Affected versionversion=7.65.0 <=7.65.0
  110. Affected versionversion=7.65.1 <=7.65.1
  111. Affected versionversion=7.65.2 <=7.65.2
  112. Affected versionversion=7.65.3 <=7.65.3
  113. Affected versionversion=7.66.0 <=7.66.0
  114. Affected versionversion=7.67.0 <=7.67.0
  115. Affected versionversion=7.68.0 <=7.68.0
  116. Affected versionversion=7.69.0 <=7.69.0
  117. Affected versionversion=7.69.1 <=7.69.1
  118. Affected versionversion=7.70.0 <=7.70.0
  119. Affected versionversion=7.71.0 <=7.71.0
  120. Affected versionversion=7.71.1 <=7.71.1
  121. Affected versionversion=7.72.0 <=7.72.0
  122. Affected versionversion=7.73.0 <=7.73.0
  123. Affected versionversion=7.74.0 <=7.74.0
  124. Affected versionversion=7.75.0 <=7.75.0
  125. Affected versionversion=7.76.0 <=7.76.0
  126. Affected versionversion=7.76.1 <=7.76.1
  127. Affected versionversion=7.77.0 <=7.77.0
  128. Affected versionversion=7.78.0 <=7.78.0
  129. Affected versionversion=7.79.0 <=7.79.0
  130. Affected versionversion=7.79.1 <=7.79.1
  131. Affected versionversion=7.80.0 <=7.80.0
  132. Affected versionversion=7.81.0 <=7.81.0
  133. Affected versionversion=7.82.0 <=7.82.0
  134. Affected versionversion=7.83.0 <=7.83.0
  135. Affected versionversion=7.83.1 <=7.83.1
  136. Affected versionversion=7.84.0 <=7.84.0
  137. Affected versionversion=7.85.0 <=7.85.0
  138. Affected versionversion=7.86.0 <=7.86.0
  139. Affected versionversion=7.87.0 <=7.87.0
  140. Affected versionversion=7.88.0 <=7.88.0
  141. Affected versionversion=7.88.1 <=7.88.1
  142. Affected versionversion=8.0.0 <=8.0.0
  143. Affected versionversion=8.0.1 <=8.0.1
  144. Affected versionversion=8.10.0 <=8.10.0
  145. Affected versionversion=8.10.1 <=8.10.1
  146. Affected versionversion=8.1.0 <=8.1.0
  147. Affected versionversion=8.11.0 <=8.11.0
  148. Affected versionversion=8.11.1 <=8.11.1
  149. Affected versionversion=8.1.1 <=8.1.1
  150. Affected versionversion=8.12.0 <=8.12.0
  151. Affected versionversion=8.12.1 <=8.12.1
  152. Affected versionversion=8.1.2 <=8.1.2
  153. Affected versionversion=8.13.0 <=8.13.0
  154. Affected versionversion=8.14.0 <=8.14.0
  155. Affected versionversion=8.14.1 <=8.14.1
  156. Affected versionversion=8.15.0 <=8.15.0
  157. Affected versionversion=8.16.0 <=8.16.0
  158. Affected versionversion=8.17.0 <=8.17.0
  159. Affected versionversion=8.18.0 <=8.18.0
  160. Affected versionversion=8.19.0 <=8.19.0
  161. Affected versionversion=8.2.0 <=8.2.0
  162. Affected versionversion=8.2.1 <=8.2.1
  163. Affected versionversion=8.3.0 <=8.3.0
  164. Affected versionversion=8.4.0 <=8.4.0
  165. Affected versionversion=8.5.0 <=8.5.0
  166. Affected versionversion=8.6.0 <=8.6.0
  167. Affected versionversion=8.7.0 <=8.7.0
  168. Affected versionversion=8.7.1 <=8.7.1
  169. Affected versionversion=8.8.0 <=8.8.0
  170. Affected versionversion=8.9.0 <=8.9.0
  171. Affected versionversion=8.9.1 <=8.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

curl · curlversion=7.10.6 <=7.10.6; version=7.10.7 <=7.10.7; version=7.10.8 <=7.10.8; version=7.11.0 <=7.11.0; version=7.11.1 <=7.11.1; version=7.11.2 <=7.11.2; version=7.12.0 <=7.12.0; version=7.12.1 <=7.12.1; version=7.12.2 <=7.12.2; version=7.12.3 <=7.12.3; version=7.13.0 <=7.13.0; version=7.13.1 <=7.13.1; version=7.13.2 <=7.13.2; version=7.14.0 <=7.14.0; version=7.14.1 <=7.14.1; version=7.15.0 <=7.15.0; version=7.15.1 <=7.15.1; version=7.15.2 <=7.15.2; version=7.15.3 <=7.15.3; version=7.15.4 <=7.15.4; version=7.15.5 <=7.15.5; version=7.16.0 <=7.16.0; version=7.16.1 <=7.16.1; version=7.16.2 <=7.16.2; version=7.16.3 <=7.16.3; version=7.16.4 <=7.16.4; version=7.17.0 <=7.17.0; version=7.17.1 <=7.17.1; version=7.18.0 <=7.18.0; version=7.18.1 <=7.18.1; version=7.18.2 <=7.18.2; version=7.19.0 <=7.19.0; version=7.19.1 <=7.19.1; version=7.19.2 <=7.19.2; version=7.19.3 <=7.19.3; version=7.19.4 <=7.19.4; version=7.19.5 <=7.19.5; version=7.19.6 <=7.19.6; version=7.19.7 <=7.19.7; version=7.20.0 <=7.20.0; version=7.20.1 <=7.20.1; version=7.21.0 <=7.21.0; version=7.21.1 <=7.21.1; version=7.21.2 <=7.21.2; version=7.21.3 <=7.21.3; version=7.21.4 <=7.21.4; version=7.21.5 <=7.21.5; version=7.21.6 <=7.21.6; version=7.21.7 <=7.21.7; version=7.22.0 <=7.22.0; version=7.23.0 <=7.23.0; version=7.23.1 <=7.23.1; version=7.24.0 <=7.24.0; version=7.25.0 <=7.25.0; version=7.26.0 <=7.26.0; version=7.27.0 <=7.27.0; version=7.28.0 <=7.28.0; version=7.28.1 <=7.28.1; version=7.29.0 <=7.29.0; version=7.30.0 <=7.30.0; version=7.31.0 <=7.31.0; version=7.32.0 <=7.32.0; version=7.33.0 <=7.33.0; version=7.34.0 <=7.34.0; version=7.35.0 <=7.35.0; version=7.36.0 <=7.36.0; version=7.37.0 <=7.37.0; version=7.37.1 <=7.37.1; version=7.38.0 <=7.38.0; version=7.39.0 <=7.39.0; version=7.40.0 <=7.40.0; version=7.41.0 <=7.41.0; version=7.42.0 <=7.42.0; version=7.42.1 <=7.42.1; version=7.43.0 <=7.43.0; version=7.44.0 <=7.44.0; version=7.45.0 <=7.45.0; version=7.46.0 <=7.46.0; version=7.47.0 <=7.47.0; version=7.47.1 <=7.47.1; version=7.48.0 <=7.48.0; version=7.49.0 <=7.49.0; version=7.49.1 <=7.49.1; version=7.50.0 <=7.50.0; version=7.50.1 <=7.50.1; version=7.50.2 <=7.50.2; version=7.50.3 <=7.50.3; version=7.51.0 <=7.51.0; version=7.52.0 <=7.52.0; version=7.52.1 <=7.52.1; version=7.53.0 <=7.53.0; version=7.53.1 <=7.53.1; version=7.54.0 <=7.54.0; version=7.54.1 <=7.54.1; version=7.55.0 <=7.55.0; version=7.55.1 <=7.55.1; version=7.56.0 <=7.56.0; version=7.56.1 <=7.56.1; version=7.57.0 <=7.57.0; version=7.58.0 <=7.58.0; version=7.59.0 <=7.59.0; version=7.60.0 <=7.60.0; version=7.61.0 <=7.61.0; version=7.61.1 <=7.61.1; version=7.62.0 <=7.62.0; version=7.63.0 <=7.63.0; version=7.64.0 <=7.64.0; version=7.64.1 <=7.64.1; version=7.65.0 <=7.65.0; version=7.65.1 <=7.65.1; version=7.65.2 <=7.65.2; version=7.65.3 <=7.65.3; version=7.66.0 <=7.66.0; version=7.67.0 <=7.67.0; version=7.68.0 <=7.68.0; version=7.69.0 <=7.69.0; version=7.69.1 <=7.69.1; version=7.70.0 <=7.70.0; version=7.71.0 <=7.71.0; version=7.71.1 <=7.71.1; version=7.72.0 <=7.72.0; version=7.73.0 <=7.73.0; version=7.74.0 <=7.74.0; version=7.75.0 <=7.75.0; version=7.76.0 <=7.76.0; version=7.76.1 <=7.76.1; version=7.77.0 <=7.77.0; version=7.78.0 <=7.78.0; version=7.79.0 <=7.79.0; version=7.79.1 <=7.79.1; version=7.80.0 <=7.80.0; version=7.81.0 <=7.81.0; version=7.82.0 <=7.82.0; version=7.83.0 <=7.83.0; version=7.83.1 <=7.83.1; version=7.84.0 <=7.84.0; version=7.85.0 <=7.85.0; version=7.86.0 <=7.86.0; version=7.87.0 <=7.87.0; version=7.88.0 <=7.88.0; version=7.88.1 <=7.88.1; version=8.0.0 <=8.0.0; version=8.0.1 <=8.0.1; version=8.10.0 <=8.10.0; version=8.10.1 <=8.10.1; version=8.1.0 <=8.1.0; version=8.11.0 <=8.11.0; version=8.11.1 <=8.11.1; version=8.1.1 <=8.1.1; version=8.12.0 <=8.12.0; version=8.12.1 <=8.12.1; version=8.1.2 <=8.1.2; version=8.13.0 <=8.13.0; version=8.14.0 <=8.14.0; version=8.14.1 <=8.14.1; version=8.15.0 <=8.15.0; version=8.16.0 <=8.16.0; version=8.17.0 <=8.17.0; version=8.18.0 <=8.18.0; version=8.19.0 <=8.19.0; version=8.2.0 <=8.2.0; version=8.2.1 <=8.2.1; version=8.3.0 <=8.3.0; version=8.4.0 <=8.4.0; version=8.5.0 <=8.5.0; version=8.6.0 <=8.6.0; version=8.7.0 <=8.7.0; version=8.7.1 <=8.7.1; version=8.8.0 <=8.8.0; version=8.9.0 <=8.9.0; version=8.9.1 <=8.9.1

Published CVSS scores

6.5CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-613Insufficient Session Expiration
CWE-305Authentication Bypass by Primary Weakness
T1078Valid Accounts

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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