wrong reuse of HTTP Negotiate connection
Summary
| CVE | CVE-2026-5545 |
|---|---|
| State | PUBLISHED |
| Assigner | curl |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-13 13:01:56 UTC |
| Updated | 2026-05-13 19:31:07 UTC |
| Description | 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... |
Risk And Classification
Primary CVSS: v3.1 6.5 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
EPSS: 0.000490000 probability, percentile 0.150540000 (date 2026-05-21)
Problem Types: CWE-613 | CWE-305 Authentication Bypass by Primary Weakness
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N |
| 3.1 | ADP | DECLARED | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N |
| 3.1 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | Secondary | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
HighPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
LowIntegrity
HighAvailability
NoneCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Curl | Curl | affected 8.19.0 8.19.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.18.0 8.18.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.17.0 8.17.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.16.0 8.16.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.15.0 8.15.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.14.1 8.14.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.14.0 8.14.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.13.0 8.13.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.12.1 8.12.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.12.0 8.12.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.11.1 8.11.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.11.0 8.11.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.10.1 8.10.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.10.0 8.10.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.9.1 8.9.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.9.0 8.9.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.8.0 8.8.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.7.1 8.7.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.7.0 8.7.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.6.0 8.6.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.5.0 8.5.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.4.0 8.4.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.3.0 8.3.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.2.1 8.2.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.2.0 8.2.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.1.2 8.1.2 semver | Not specified |
| CNA | Curl | Curl | affected 8.1.1 8.1.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.1.0 8.1.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.0.1 8.0.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.0.0 8.0.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.88.1 7.88.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.88.0 7.88.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.87.0 7.87.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.86.0 7.86.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.85.0 7.85.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.84.0 7.84.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.83.1 7.83.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.83.0 7.83.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.82.0 7.82.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.81.0 7.81.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.80.0 7.80.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.79.1 7.79.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.79.0 7.79.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.78.0 7.78.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.77.0 7.77.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.76.1 7.76.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.76.0 7.76.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.75.0 7.75.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.74.0 7.74.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.73.0 7.73.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.72.0 7.72.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.71.1 7.71.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.71.0 7.71.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.70.0 7.70.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.69.1 7.69.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.69.0 7.69.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.68.0 7.68.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.67.0 7.67.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.66.0 7.66.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.65.3 7.65.3 semver | Not specified |
| CNA | Curl | Curl | affected 7.65.2 7.65.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.65.1 7.65.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.65.0 7.65.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.64.1 7.64.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.64.0 7.64.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.63.0 7.63.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.62.0 7.62.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.61.1 7.61.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.61.0 7.61.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.60.0 7.60.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.59.0 7.59.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.58.0 7.58.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.57.0 7.57.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.56.1 7.56.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.56.0 7.56.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.55.1 7.55.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.55.0 7.55.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.54.1 7.54.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.54.0 7.54.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.53.1 7.53.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.53.0 7.53.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.52.1 7.52.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.52.0 7.52.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.51.0 7.51.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.50.3 7.50.3 semver | Not specified |
| CNA | Curl | Curl | affected 7.50.2 7.50.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.50.1 7.50.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.50.0 7.50.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.49.1 7.49.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.49.0 7.49.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.48.0 7.48.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.47.1 7.47.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.47.0 7.47.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.46.0 7.46.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.45.0 7.45.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.44.0 7.44.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.43.0 7.43.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.42.1 7.42.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.42.0 7.42.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.41.0 7.41.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.40.0 7.40.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.39.0 7.39.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.38.0 7.38.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.37.1 7.37.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.37.0 7.37.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.36.0 7.36.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.35.0 7.35.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.34.0 7.34.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.33.0 7.33.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.32.0 7.32.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.31.0 7.31.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.30.0 7.30.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.29.0 7.29.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.28.1 7.28.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.28.0 7.28.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.27.0 7.27.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.26.0 7.26.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.25.0 7.25.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.24.0 7.24.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.23.1 7.23.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.23.0 7.23.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.22.0 7.22.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.21.7 7.21.7 semver | Not specified |
| CNA | Curl | Curl | affected 7.21.6 7.21.6 semver | Not specified |
| CNA | Curl | Curl | affected 7.21.5 7.21.5 semver | Not specified |
| CNA | Curl | Curl | affected 7.21.4 7.21.4 semver | Not specified |
| CNA | Curl | Curl | affected 7.21.3 7.21.3 semver | Not specified |
| CNA | Curl | Curl | affected 7.21.2 7.21.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.21.1 7.21.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.21.0 7.21.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.20.1 7.20.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.20.0 7.20.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.19.7 7.19.7 semver | Not specified |
| CNA | Curl | Curl | affected 7.19.6 7.19.6 semver | Not specified |
| CNA | Curl | Curl | affected 7.19.5 7.19.5 semver | Not specified |
| CNA | Curl | Curl | affected 7.19.4 7.19.4 semver | Not specified |
| CNA | Curl | Curl | affected 7.19.3 7.19.3 semver | Not specified |
| CNA | Curl | Curl | affected 7.19.2 7.19.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.19.1 7.19.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.19.0 7.19.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.18.2 7.18.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.18.1 7.18.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.18.0 7.18.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.17.1 7.17.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.17.0 7.17.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.16.4 7.16.4 semver | Not specified |
| CNA | Curl | Curl | affected 7.16.3 7.16.3 semver | Not specified |
| CNA | Curl | Curl | affected 7.16.2 7.16.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.16.1 7.16.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.16.0 7.16.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.15.5 7.15.5 semver | Not specified |
| CNA | Curl | Curl | affected 7.15.4 7.15.4 semver | Not specified |
| CNA | Curl | Curl | affected 7.15.3 7.15.3 semver | Not specified |
| CNA | Curl | Curl | affected 7.15.2 7.15.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.15.1 7.15.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.15.0 7.15.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.14.1 7.14.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.14.0 7.14.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.13.2 7.13.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.13.1 7.13.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.13.0 7.13.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.12.3 7.12.3 semver | Not specified |
| CNA | Curl | Curl | affected 7.12.2 7.12.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.12.1 7.12.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.12.0 7.12.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.11.2 7.11.2 semver | Not specified |
| CNA | Curl | Curl | affected 7.11.1 7.11.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.11.0 7.11.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.10.8 7.10.8 semver | Not specified |
| CNA | Curl | Curl | affected 7.10.7 7.10.7 semver | Not specified |
| CNA | Curl | Curl | affected 7.10.6 7.10.6 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| hackerone.com/reports/3642555 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | hackerone.com | Exploit, Issue Tracking, Third Party Advisory |
| curl.se/docs/CVE-2026-5545.json | 2499f714-1537-4658-8207-48ae4bb9eae9 | curl.se | Vendor Advisory |
| curl.se/docs/CVE-2026-5545.html | 2499f714-1537-4658-8207-48ae4bb9eae9 | curl.se | Patch, Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Quac Tran and Ngoc Hieu (en)
CNA: Stefan Eissing (en)
There are currently no legacy QID mappings associated with this CVE.