CVE-2026-8286Public exploitNetwork attack vector

STARTTLS traffic compromise via mismatched connection reuse

Published Jul 3, 2026 · Updated Jul 3, 2026

Improper certificate validation in curl 7.30.0 through 8.20.0 allows remote authenticated users to read or alter STARTTLS traffic. The connection-reuse path in lib/url.c checks TLS configuration only for initially encrypted schemes, skipping the check when cleartext IMAP, POP3, SMTP, FTP, or LDAP transfers upgrade to TLS. Exploitation requires a reusable live connection and a later transfer to the same destination with different TLS settings; availability is unaffected.

CVSS severity8.1
High
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in curl 7.30.0 through 8.20.0 allows remote authenticated users to read or alter STARTTLS traffic. The connection-reuse path in lib/url.c checks TLS configuration only for initially encrypted schemes, skipping the check when cleartext IMAP, POP3, SMTP, FTP, or LDAP transfers upgrade to TLS. Exploitation requires a reusable live connection and a later transfer to the same destination with different TLS settings; availability is unaffected.

The record

CVE
CVE-2026-8286
Published
Jul 3, 2026
Updated
Jul 3, 2026
Vendor
curl
Product
curl
Classifications
CWE-295, T1557
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 3, 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=7.30.0 <=7.30.0
  2. Affected versionversion=7.31.0 <=7.31.0
  3. Affected versionversion=7.32.0 <=7.32.0
  4. Affected versionversion=7.33.0 <=7.33.0
  5. Affected versionversion=7.34.0 <=7.34.0
  6. Affected versionversion=7.35.0 <=7.35.0
  7. Affected versionversion=7.36.0 <=7.36.0
  8. Affected versionversion=7.37.0 <=7.37.0
  9. Affected versionversion=7.37.1 <=7.37.1
  10. Affected versionversion=7.38.0 <=7.38.0
  11. Affected versionversion=7.39.0 <=7.39.0
  12. Affected versionversion=7.40.0 <=7.40.0
  13. Affected versionversion=7.41.0 <=7.41.0
  14. Affected versionversion=7.42.0 <=7.42.0
  15. Affected versionversion=7.42.1 <=7.42.1
  16. Affected versionversion=7.43.0 <=7.43.0
  17. Affected versionversion=7.44.0 <=7.44.0
  18. Affected versionversion=7.45.0 <=7.45.0
  19. Affected versionversion=7.46.0 <=7.46.0
  20. Affected versionversion=7.47.0 <=7.47.0
  21. Affected versionversion=7.47.1 <=7.47.1
  22. Affected versionversion=7.48.0 <=7.48.0
  23. Affected versionversion=7.49.0 <=7.49.0
  24. Affected versionversion=7.49.1 <=7.49.1
  25. Affected versionversion=7.50.0 <=7.50.0
  26. Affected versionversion=7.50.1 <=7.50.1
  27. Affected versionversion=7.50.2 <=7.50.2
  28. Affected versionversion=7.50.3 <=7.50.3
  29. Affected versionversion=7.51.0 <=7.51.0
  30. Affected versionversion=7.52.0 <=7.52.0
  31. Affected versionversion=7.52.1 <=7.52.1
  32. Affected versionversion=7.53.0 <=7.53.0
  33. Affected versionversion=7.53.1 <=7.53.1
  34. Affected versionversion=7.54.0 <=7.54.0
  35. Affected versionversion=7.54.1 <=7.54.1
  36. Affected versionversion=7.55.0 <=7.55.0
  37. Affected versionversion=7.55.1 <=7.55.1
  38. Affected versionversion=7.56.0 <=7.56.0
  39. Affected versionversion=7.56.1 <=7.56.1
  40. Affected versionversion=7.57.0 <=7.57.0
  41. Affected versionversion=7.58.0 <=7.58.0
  42. Affected versionversion=7.59.0 <=7.59.0
  43. Affected versionversion=7.60.0 <=7.60.0
  44. Affected versionversion=7.61.0 <=7.61.0
  45. Affected versionversion=7.61.1 <=7.61.1
  46. Affected versionversion=7.62.0 <=7.62.0
  47. Affected versionversion=7.63.0 <=7.63.0
  48. Affected versionversion=7.64.0 <=7.64.0
  49. Affected versionversion=7.64.1 <=7.64.1
  50. Affected versionversion=7.65.0 <=7.65.0
  51. Affected versionversion=7.65.1 <=7.65.1
  52. Affected versionversion=7.65.2 <=7.65.2
  53. Affected versionversion=7.65.3 <=7.65.3
  54. Affected versionversion=7.66.0 <=7.66.0
  55. Affected versionversion=7.67.0 <=7.67.0
  56. Affected versionversion=7.68.0 <=7.68.0
  57. Affected versionversion=7.69.0 <=7.69.0
  58. Affected versionversion=7.69.1 <=7.69.1
  59. Affected versionversion=7.70.0 <=7.70.0
  60. Affected versionversion=7.71.0 <=7.71.0
  61. Affected versionversion=7.71.1 <=7.71.1
  62. Affected versionversion=7.72.0 <=7.72.0
  63. Affected versionversion=7.73.0 <=7.73.0
  64. Affected versionversion=7.74.0 <=7.74.0
  65. Affected versionversion=7.75.0 <=7.75.0
  66. Affected versionversion=7.76.0 <=7.76.0
  67. Affected versionversion=7.76.1 <=7.76.1
  68. Affected versionversion=7.77.0 <=7.77.0
  69. Affected versionversion=7.78.0 <=7.78.0
  70. Affected versionversion=7.79.0 <=7.79.0
  71. Affected versionversion=7.79.1 <=7.79.1
  72. Affected versionversion=7.80.0 <=7.80.0
  73. Affected versionversion=7.81.0 <=7.81.0
  74. Affected versionversion=7.82.0 <=7.82.0
  75. Affected versionversion=7.83.0 <=7.83.0
  76. Affected versionversion=7.83.1 <=7.83.1
  77. Affected versionversion=7.84.0 <=7.84.0
  78. Affected versionversion=7.85.0 <=7.85.0
  79. Affected versionversion=7.86.0 <=7.86.0
  80. Affected versionversion=7.87.0 <=7.87.0
  81. Affected versionversion=7.88.0 <=7.88.0
  82. Affected versionversion=7.88.1 <=7.88.1
  83. Affected versionversion=8.0.0 <=8.0.0
  84. Affected versionversion=8.0.1 <=8.0.1
  85. Affected versionversion=8.10.0 <=8.10.0
  86. Affected versionversion=8.10.1 <=8.10.1
  87. Affected versionversion=8.1.0 <=8.1.0
  88. Affected versionversion=8.11.0 <=8.11.0
  89. Affected versionversion=8.11.1 <=8.11.1
  90. Affected versionversion=8.1.1 <=8.1.1
  91. Affected versionversion=8.12.0 <=8.12.0
  92. Affected versionversion=8.12.1 <=8.12.1
  93. Affected versionversion=8.1.2 <=8.1.2
  94. Affected versionversion=8.13.0 <=8.13.0
  95. Affected versionversion=8.14.0 <=8.14.0
  96. Affected versionversion=8.14.1 <=8.14.1
  97. Affected versionversion=8.15.0 <=8.15.0
  98. Affected versionversion=8.16.0 <=8.16.0
  99. Affected versionversion=8.17.0 <=8.17.0
  100. Affected versionversion=8.18.0 <=8.18.0
  101. Affected versionversion=8.19.0 <=8.19.0
  102. Affected versionversion=8.20.0 <=8.20.0
  103. Affected versionversion=8.2.0 <=8.2.0
  104. Affected versionversion=8.2.1 <=8.2.1
  105. Affected versionversion=8.3.0 <=8.3.0
  106. Affected versionversion=8.4.0 <=8.4.0
  107. Affected versionversion=8.5.0 <=8.5.0
  108. Affected versionversion=8.6.0 <=8.6.0
  109. Affected versionversion=8.7.0 <=8.7.0
  110. Affected versionversion=8.7.1 <=8.7.1
  111. Affected versionversion=8.8.0 <=8.8.0
  112. Affected versionversion=8.9.0 <=8.9.0
  113. Affected versionversion=8.9.1 <=8.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

curl · curlversion=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=8.20.0 <=8.20.0; 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

5.4OracleCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
8.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

Public exploit references

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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