CVE-2026-8927

When reusing a libcurl handle for sequential transfers driven by environment-variable proxy configuration, libcurl fails to clear the proxy authentication state between requests. Specifically, if the initial transfer authenticates against `proxyA` using Digest auth, a subsequent transfer routed through `proxyB` erroneously leaks the `Proxy-Authorization:` header intended solely for `proxyA`.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://curl.se/docs/CVE-2026-8927.html	Patch Vendor Advisory
https://curl.se/docs/CVE-2026-8927.json	Vendor Advisory
https://hackerone.com/reports/3744543	Exploit Issue Tracking Third Party Advisory
https://hackerone.com/reports/3744543	Exploit Issue Tracking Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-07-03 07:16

Updated : 2026-09-15 07:16

NVD link : CVE-2026-8927

Mitre link : CVE-2026-8927

CVE.ORG link : CVE-2026-8927

JSON object : View

Products Affected

haxx

curl

CWE

CWE-294

Authentication Bypass by Capture-replay

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"affected", "version": "7.12.2"}, {"status": "affected", "version": "7.12.1"}, {"status": "affected", "version": "7.12.0"}], "defaultStatus": "unaffected"}]}], "published": "2026-07-03T07:16:25.123", "references": [{"url": "https://curl.se/docs/CVE-2026-8927.html", "tags": ["Patch", "Vendor Advisory"], "source": "2499f714-1537-4658-8207-48ae4bb9eae9"}, {"url": "https://curl.se/docs/CVE-2026-8927.json", "tags": ["Vendor Advisory"], "source": "2499f714-1537-4658-8207-48ae4bb9eae9"}, {"url": "https://hackerone.com/reports/3744543", "tags": ["Exploit", "Issue Tracking", "Third Party Advisory"], "source": "2499f714-1537-4658-8207-48ae4bb9eae9"}, {"url": "https://hackerone.com/reports/3744543", "tags": ["Exploit", "Issue Tracking", "Third Party Advisory"], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}], "vulnStatus": "Modified", "weaknesses": [{"type": "Secondary", "source": "2499f714-1537-4658-8207-48ae4bb9eae9", "description": [{"lang": "en", "value": "CWE-294"}]}, {"type": "Primary", "source": "nvd@nist.gov", "description": [{"lang": "en", "value": "CWE-294"}]}], "descriptions": [{"lang": "en", "value": "When reusing a libcurl handle for sequential transfers driven by\nenvironment-variable proxy configuration, libcurl fails to clear the proxy\nauthentication state between requests. Specifically, if the initial transfer\nauthenticates against `proxyA` using Digest auth, a subsequent transfer routed\nthrough `proxyB` erroneously leaks the `Proxy-Authorization:` header intended\nsolely for `proxyA`."}], "lastModified": "2026-09-15T07:16:33.157", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "30556268-32BA-489F-B0EA-E0A7EE5356BE", "versionEndExcluding": "8.21.0", "versionStartIncluding": "7.12.0"}], "operator": "OR"}]}], "sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9"}