CVE-2026-5545 (GCVE-0-2026-5545)
Vulnerability from cvelistv5 – Published: 2026-05-13 08:27 – Updated: 2026-09-15 06:02
VLAI
EPSS
VEX
Title
wrong reuse of HTTP Negotiate connection
Summary
libcurl might in some circumstances reuse the wrong connection when asked to
do an authenticated HTTP(S) request after a Negotiate-authenticated one, when
both use the same host.
libcurl features a pool of recent connections so that subsequent requests can
reuse an existing connection to avoid overhead.
When reusing a connection a range of criteria must be met. Due to a logical
error in the code, a request that was issued by an application could
wrongfully reuse an existing connection to the same server that was
authenticated using different credentials.
An application that first uses Negotiate authentication to a server with
`user1:password1` and then does another operation to the same server asking
for any authentication method but for `user2:password2` (while the previous
connection is still alive) - the second request gets confused and wrongly
reuses the same connection and sends the new request over that connection
thinking it uses a mix of user1's and user2's credentials when it is in fact
still using the connection authenticated for user1...
Severity
6.5 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-13 17:46 UTC
CWE
- CWE-305 - Authentication Bypass by Primary Weakness
Assigner
References
Impacted products
3 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| curl | curl |
Affected:
7.10.6 , < 8.14.2
(semver)
Affected: 8.15.0 , < 8.16.1 (semver) Affected: 8.17.0 , < 8.20.0 (semver) |
guessed | |
| curl | curl |
Affected:
e56ae1426cb7a0a4a427cf8d6099a821fdaae428 , < 33e43985b8f3b9e66691d06e70be0395849856cd
(git)
|
guessed | |
| curl | curl |
Affected:
8.19.0
Affected: 8.18.0 Affected: 8.17.0 Affected: 8.16.0 Affected: 8.15.0 Affected: 8.14.1 Affected: 8.14.0 Affected: 8.13.0 Affected: 8.12.1 Affected: 8.12.0 Affected: 8.11.1 Affected: 8.11.0 Affected: 8.10.1 Affected: 8.10.0 Affected: 8.9.1 Affected: 8.9.0 Affected: 8.8.0 Affected: 8.7.1 Affected: 8.7.0 Affected: 8.6.0 Affected: 8.5.0 Affected: 8.4.0 Affected: 8.3.0 Affected: 8.2.1 Affected: 8.2.0 Affected: 8.1.2 Affected: 8.1.1 Affected: 8.1.0 Affected: 8.0.1 Affected: 8.0.0 Affected: 7.88.1 Affected: 7.88.0 Affected: 7.87.0 Affected: 7.86.0 Affected: 7.85.0 Affected: 7.84.0 Affected: 7.83.1 Affected: 7.83.0 Affected: 7.82.0 Affected: 7.81.0 Affected: 7.80.0 Affected: 7.79.1 Affected: 7.79.0 Affected: 7.78.0 Affected: 7.77.0 Affected: 7.76.1 Affected: 7.76.0 Affected: 7.75.0 Affected: 7.74.0 Affected: 7.73.0 Affected: 7.72.0 Affected: 7.71.1 Affected: 7.71.0 Affected: 7.70.0 Affected: 7.69.1 Affected: 7.69.0 Affected: 7.68.0 Affected: 7.67.0 Affected: 7.66.0 Affected: 7.65.3 Affected: 7.65.2 Affected: 7.65.1 Affected: 7.65.0 Affected: 7.64.1 Affected: 7.64.0 Affected: 7.63.0 Affected: 7.62.0 Affected: 7.61.1 Affected: 7.61.0 Affected: 7.60.0 Affected: 7.59.0 Affected: 7.58.0 Affected: 7.57.0 Affected: 7.56.1 Affected: 7.56.0 Affected: 7.55.1 Affected: 7.55.0 Affected: 7.54.1 Affected: 7.54.0 Affected: 7.53.1 Affected: 7.53.0 Affected: 7.52.1 Affected: 7.52.0 Affected: 7.51.0 Affected: 7.50.3 Affected: 7.50.2 Affected: 7.50.1 Affected: 7.50.0 Affected: 7.49.1 Affected: 7.49.0 Affected: 7.48.0 Affected: 7.47.1 Affected: 7.47.0 Affected: 7.46.0 Affected: 7.45.0 Affected: 7.44.0 Affected: 7.43.0 Affected: 7.42.1 Affected: 7.42.0 Affected: 7.41.0 Affected: 7.40.0 Affected: 7.39.0 Affected: 7.38.0 Affected: 7.37.1 Affected: 7.37.0 Affected: 7.36.0 Affected: 7.35.0 Affected: 7.34.0 Affected: 7.33.0 Affected: 7.32.0 Affected: 7.31.0 Affected: 7.30.0 Affected: 7.29.0 Affected: 7.28.1 Affected: 7.28.0 Affected: 7.27.0 Affected: 7.26.0 Affected: 7.25.0 Affected: 7.24.0 Affected: 7.23.1 Affected: 7.23.0 Affected: 7.22.0 Affected: 7.21.7 Affected: 7.21.6 Affected: 7.21.5 Affected: 7.21.4 Affected: 7.21.3 Affected: 7.21.2 Affected: 7.21.1 Affected: 7.21.0 Affected: 7.20.1 Affected: 7.20.0 Affected: 7.19.7 Affected: 7.19.6 Affected: 7.19.5 Affected: 7.19.4 Affected: 7.19.3 Affected: 7.19.2 Affected: 7.19.1 Affected: 7.19.0 Affected: 7.18.2 Affected: 7.18.1 Affected: 7.18.0 Affected: 7.17.1 Affected: 7.17.0 Affected: 7.16.4 Affected: 7.16.3 Affected: 7.16.2 Affected: 7.16.1 Affected: 7.16.0 Affected: 7.15.5 Affected: 7.15.4 Affected: 7.15.3 Affected: 7.15.2 Affected: 7.15.1 Affected: 7.15.0 Affected: 7.14.1 Affected: 7.14.0 Affected: 7.13.2 Affected: 7.13.1 Affected: 7.13.0 Affected: 7.12.3 Affected: 7.12.2 Affected: 7.12.1 Affected: 7.12.0 Affected: 7.11.2 Affected: 7.11.1 Affected: 7.11.0 Affected: 7.10.8 Affected: 7.10.7 Affected: 7.10.6 |
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
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"attackComplexity": "HIGH",
"attackVector": "NETWORK",
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"confidentialityImpact": "LOW",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N",
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"timestamp": "2026-05-13T17:46:36.115262Z",
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"tags": [
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"url": "https://hackerone.com/reports/3642555"
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"title": "CISA ADP Vulnrichment"
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"version": "8.17.0"
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"version": "8.16.0"
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"version": "8.15.0"
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"version": "8.14.0"
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"version": "8.13.0"
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"version": "8.12.0"
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"version": "8.3.0"
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"status": "affected",
"version": "8.2.1"
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"version": "8.2.0"
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"status": "affected",
"version": "8.1.2"
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"status": "affected",
"version": "8.1.1"
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"version": "8.1.0"
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"version": "8.0.1"
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"version": "7.88.1"
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"status": "affected",
"version": "7.79.0"
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{
"status": "affected",
"version": "7.78.0"
},
{
"status": "affected",
"version": "7.77.0"
},
{
"status": "affected",
"version": "7.76.1"
},
{
"status": "affected",
"version": "7.76.0"
},
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"status": "affected",
"version": "7.75.0"
},
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"status": "affected",
"version": "7.74.0"
},
{
"status": "affected",
"version": "7.73.0"
},
{
"status": "affected",
"version": "7.72.0"
},
{
"status": "affected",
"version": "7.71.1"
},
{
"status": "affected",
"version": "7.71.0"
},
{
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"version": "7.70.0"
},
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"version": "7.69.1"
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"status": "affected",
"version": "7.69.0"
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"version": "7.68.0"
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{
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"version": "7.65.3"
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"version": "7.62.0"
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"version": "7.60.0"
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"version": "7.51.0"
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"status": "affected",
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"status": "affected",
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"version": "7.50.0"
},
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},
{
"status": "affected",
"version": "7.49.0"
},
{
"status": "affected",
"version": "7.48.0"
},
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"status": "affected",
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"status": "affected",
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"status": "affected",
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"version": "7.44.0"
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"version": "7.43.0"
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"version": "7.42.1"
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{
"status": "affected",
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},
{
"status": "affected",
"version": "7.32.0"
},
{
"status": "affected",
"version": "7.31.0"
},
{
"status": "affected",
"version": "7.30.0"
},
{
"status": "affected",
"version": "7.29.0"
},
{
"status": "affected",
"version": "7.28.1"
},
{
"status": "affected",
"version": "7.28.0"
},
{
"status": "affected",
"version": "7.27.0"
},
{
"status": "affected",
"version": "7.26.0"
},
{
"status": "affected",
"version": "7.25.0"
},
{
"status": "affected",
"version": "7.24.0"
},
{
"status": "affected",
"version": "7.23.1"
},
{
"status": "affected",
"version": "7.23.0"
},
{
"status": "affected",
"version": "7.22.0"
},
{
"status": "affected",
"version": "7.21.7"
},
{
"status": "affected",
"version": "7.21.6"
},
{
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"version": "7.21.5"
},
{
"status": "affected",
"version": "7.21.4"
},
{
"status": "affected",
"version": "7.21.3"
},
{
"status": "affected",
"version": "7.21.2"
},
{
"status": "affected",
"version": "7.21.1"
},
{
"status": "affected",
"version": "7.21.0"
},
{
"status": "affected",
"version": "7.20.1"
},
{
"status": "affected",
"version": "7.20.0"
},
{
"status": "affected",
"version": "7.19.7"
},
{
"status": "affected",
"version": "7.19.6"
},
{
"status": "affected",
"version": "7.19.5"
},
{
"status": "affected",
"version": "7.19.4"
},
{
"status": "affected",
"version": "7.19.3"
},
{
"status": "affected",
"version": "7.19.2"
},
{
"status": "affected",
"version": "7.19.1"
},
{
"status": "affected",
"version": "7.19.0"
},
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"status": "affected",
"version": "7.18.2"
},
{
"status": "affected",
"version": "7.18.1"
},
{
"status": "affected",
"version": "7.18.0"
},
{
"status": "affected",
"version": "7.17.1"
},
{
"status": "affected",
"version": "7.17.0"
},
{
"status": "affected",
"version": "7.16.4"
},
{
"status": "affected",
"version": "7.16.3"
},
{
"status": "affected",
"version": "7.16.2"
},
{
"status": "affected",
"version": "7.16.1"
},
{
"status": "affected",
"version": "7.16.0"
},
{
"status": "affected",
"version": "7.15.5"
},
{
"status": "affected",
"version": "7.15.4"
},
{
"status": "affected",
"version": "7.15.3"
},
{
"status": "affected",
"version": "7.15.2"
},
{
"status": "affected",
"version": "7.15.1"
},
{
"status": "affected",
"version": "7.15.0"
},
{
"status": "affected",
"version": "7.14.1"
},
{
"status": "affected",
"version": "7.14.0"
},
{
"status": "affected",
"version": "7.13.2"
},
{
"status": "affected",
"version": "7.13.1"
},
{
"status": "affected",
"version": "7.13.0"
},
{
"status": "affected",
"version": "7.12.3"
},
{
"status": "affected",
"version": "7.12.2"
},
{
"status": "affected",
"version": "7.12.1"
},
{
"status": "affected",
"version": "7.12.0"
},
{
"status": "affected",
"version": "7.11.2"
},
{
"status": "affected",
"version": "7.11.1"
},
{
"status": "affected",
"version": "7.11.0"
},
{
"status": "affected",
"version": "7.10.8"
},
{
"status": "affected",
"version": "7.10.7"
},
{
"status": "affected",
"version": "7.10.6"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Quac Tran and Ngoc Hieu"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Stefan Eissing"
}
],
"descriptions": [
{
"lang": "en",
"value": "libcurl might in some circumstances reuse the wrong connection when asked to\ndo an authenticated HTTP(S) request after a Negotiate-authenticated one, when\nboth use the same host.\n\nlibcurl features a pool of recent connections so that subsequent requests can\nreuse an existing connection to avoid overhead.\n\nWhen reusing a connection a range of criteria must be met. Due to a logical\nerror in the code, a request that was issued by an application could\nwrongfully reuse an existing connection to the same server that was\nauthenticated using different credentials.\n\nAn application that first uses Negotiate authentication to a server with\n`user1:password1` and then does another operation to the same server asking\nfor any authentication method but for `user2:password2` (while the previous\nconnection is still alive) - the second request gets confused and wrongly\nreuses the same connection and sends the new request over that connection\nthinking it uses a mix of user1\u0027s and user2\u0027s credentials when it is in fact\nstill using the connection authenticated for user1..."
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-305",
"description": "Authentication Bypass by Primary Weakness",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-15T06:02:59.285Z",
"orgId": "2499f714-1537-4658-8207-48ae4bb9eae9",
"shortName": "curl"
},
"references": [
{
"url": "https://curl.se/docs/CVE-2026-5545.json"
},
{
"url": "https://curl.se/docs/CVE-2026-5545.html"
},
{
"url": "https://hackerone.com/reports/3642555"
}
],
"title": "wrong reuse of HTTP Negotiate connection",
"x_generator": {
"engine": "cvelib 1.8.0"
},
"x_osv": {
"affected": [
{
"ranges": [
{
"events": [
{
"introduced": "7.10.6"
},
{
"fixed": "8.14.2"
},
{
"introduced": "8.15.0"
},
{
"fixed": "8.16.1"
},
{
"introduced": "8.17.0"
},
{
"fixed": "8.20.0"
}
],
"type": "SEMVER"
},
{
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"credits": [
{
"name": "Quac Tran and Ngoc Hieu",
"type": "finder"
},
{
"name": "Stefan Eissing",
"type": "remediation developer"
}
],
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"id": "CWE-305"
},
"URL": "https://curl.se/docs/CVE-2026-5545.json",
"affects": "both",
"issue": "https://hackerone.com/reports/3642555",
"last_affected": "8.19.0",
"package": "curl",
"severity": "Medium",
"www": "https://curl.se/docs/CVE-2026-5545.html"
},
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"id": "CURL-CVE-2026-5545",
"modified": "2026-09-07T10:34:51.00Z",
"published": "2026-04-29T08:00:00.00Z",
"schema_version": "1.5.0",
"summary": "wrong reuse of HTTP Negotiate connection"
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"value": "libcurl might in some circumstances reuse the wrong connection when asked to\ndo an authenticated HTTP(S) request after a Negotiate-authenticated one, when\nboth use the same host.\n\nlibcurl features a pool of recent connections so that subsequent requests can\nreuse an existing connection to avoid overhead.\n\nWhen reusing a connection a range of criteria must be met. Due to a logical\nerror in the code, a request that was issued by an application could\nwrongfully reuse an existing connection to the same server that was\nauthenticated using different credentials.\n\nAn application that first uses Negotiate authentication to a server with\n`user1:password1` and then does another operation to the same server asking\nfor any authentication method but for `user2:password2` (while the previous\nconnection is still alive) - the second request gets confused and wrongly\nreuses the same connection and sends the new request over that connection\nthinking it uses a mix of user1\u0027s and user2\u0027s credentials when it is in fact\nstill using the connection authenticated for user1..."
}
],
"id": "CVE-2026-5545",
"lastModified": "2026-09-15T07:16:28.633",
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"8.1.1",
"8.1.0",
"8.0.1",
"8.0.0",
"7.88.1",
"7.88.0",
"7.87.0",
"7.86.0",
"7.85.0",
"7.84.0",
"7.83.1",
"7.83.0",
"7.82.0",
"7.81.0",
"7.80.0",
"7.79.1",
"7.79.0",
"7.78.0",
"7.77.0",
"7.76.1",
"7.76.0",
"7.75.0",
"7.74.0",
"7.73.0",
"7.72.0",
"7.71.1",
"7.71.0",
"7.70.0",
"7.69.1",
"7.69.0",
"7.68.0",
"7.67.0",
"7.66.0",
"7.65.3",
"7.65.2",
"7.65.1",
"7.65.0",
"7.64.1",
"7.64.0",
"7.63.0",
"7.62.0",
"7.61.1",
"7.61.0",
"7.60.0",
"7.59.0",
"7.58.0",
"7.57.0",
"7.56.1",
"7.56.0",
"7.55.1",
"7.55.0",
"7.54.1",
"7.54.0",
"7.53.1",
"7.53.0",
"7.52.1",
"7.52.0",
"7.51.0",
"7.50.3",
"7.50.2",
"7.50.1",
"7.50.0",
"7.49.1",
"7.49.0",
"7.48.0",
"7.47.1",
"7.47.0",
"7.46.0",
"7.45.0",
"7.44.0",
"7.43.0",
"7.42.1",
"7.42.0",
"7.41.0",
"7.40.0",
"7.39.0",
"7.38.0",
"7.37.1",
"7.37.0",
"7.36.0",
"7.35.0",
"7.34.0",
"7.33.0",
"7.32.0",
"7.31.0",
"7.30.0",
"7.29.0",
"7.28.1",
"7.28.0",
"7.27.0",
"7.26.0",
"7.25.0",
"7.24.0",
"7.23.1",
"7.23.0",
"7.22.0",
"7.21.7",
"7.21.6",
"7.21.5",
"7.21.4",
"7.21.3",
"7.21.2",
"7.21.1",
"7.21.0",
"7.20.1",
"7.20.0",
"7.19.7",
"7.19.6",
"7.19.5",
"7.19.4",
"7.19.3",
"7.19.2",
"7.19.1",
"7.19.0",
"7.18.2",
"7.18.1",
"7.18.0",
"7.17.1",
"7.17.0",
"7.16.4",
"7.16.3",
"7.16.2",
"7.16.1",
"7.16.0",
"7.15.5",
"7.15.4",
"7.15.3",
"7.15.2",
"7.15.1",
"7.15.0",
"7.14.1",
"7.14.0",
"7.13.2",
"7.13.1",
"7.13.0",
"7.12.3",
"7.12.2",
"7.12.1",
"7.12.0",
"7.11.2",
"7.11.1",
"7.11.0",
"7.10.8",
"7.10.7",
"7.10.6"
]
}
],
"aliases": [
"CVE-2026-5545"
],
"credits": [
{
"name": "Quac Tran and Ngoc Hieu",
"type": "finder"
},
{
"name": "Stefan Eissing",
"type": "remediation developer"
}
],
"database_specific": {
"CWE": {
"desc": "Authentication Bypass by Primary Weakness",
"id": "CWE-305"
},
"URL": "https://curl.se/docs/CVE-2026-5545.json",
"affects": "both",
"issue": "https://hackerone.com/reports/3642555",
"last_affected": "8.19.0",
"package": "curl",
"severity": "Medium",
"www": "https://curl.se/docs/CVE-2026-5545.html"
},
"details": "libcurl might in some circumstances reuse the wrong connection when asked to\ndo an authenticated HTTP(S) request after a Negotiate-authenticated one, when\nboth use the same host.\n\nlibcurl features a pool of recent connections so that subsequent requests can\nreuse an existing connection to avoid overhead.\n\nWhen reusing a connection a range of criteria must be met. Due to a logical\nerror in the code, a request that was issued by an application could\nwrongfully reuse an existing connection to the same server that was\nauthenticated using different credentials.\n\nAn application that first uses Negotiate authentication to a server with\n`user1:password1` and then does another operation to the same server asking\nfor any authentication method but for `user2:password2` (while the previous\nconnection is still alive) - the second request gets confused and wrongly\nreuses the same connection and sends the new request over that connection\nthinking it uses a mix of user1\u0027s and user2\u0027s credentials when it is in fact\nstill using the connection authenticated for user1...",
"id": "CURL-CVE-2026-5545",
"modified": "2026-09-07T10:34:51.00Z",
"published": "2026-04-29T08:00:00.00Z",
"schema_version": "1.5.0",
"summary": "wrong reuse of HTTP Negotiate connection"
}
}
},
"cveMetadata": {
"assignerOrgId": "2499f714-1537-4658-8207-48ae4bb9eae9",
"assignerShortName": "curl",
"cveId": "CVE-2026-5545",
"datePublished": "2026-05-13T08:27:26.065Z",
"dateReserved": "2026-04-04T12:10:07.125Z",
"dateUpdated": "2026-09-15T06:02:59.285Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.