CVE-2026-86409

Setting `CURLOPT_AWS_SIGV4` to NULL but does not disable SigV4 authentication, contrary to expectations and documentation. A subsequent transfer on the same handle still sends an `Authorization: AWS4-HMAC-SHA256` header to whatever URL isset next, leaking state information.

CVSS v3 8.1 HIGH

8.1^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.2 / Impact : 5.9

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://curl.se/docs/CVE-2026-86409.html
https://curl.se/docs/CVE-2026-86409.json
https://hackerone.com/reports/3973135
https://hackerone.com/reports/3973135

Configurations

No configuration.

History

29 Oct 2026, 19:17

Type	Values Removed	Values Added
CWE		CWE-201
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 8.1
References	~~() https://hackerone.com/reports/3973135 -~~	() https://hackerone.com/reports/3973135 -

20 Oct 2026, 20:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-20 20:17

Updated : 2026-10-29 19:17

NVD link : CVE-2026-86409

Mitre link : CVE-2026-86409

CVE.ORG link : CVE-2026-86409

JSON object : View

Products Affected

No product.

CWE

CWE-201

Insertion of Sensitive Information Into Sent Data

{"id": "CVE-2026-86409", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-86409", "role": "CISA Coordinator", "options": [{"exploitation": "poc"}, {"automatable": "no"}, {"technicalImpact": "total"}], "version": "2.0.3", "timestamp": "2026-10-29T18:33:46.064413Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 8.1, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 5.9, "exploitabilityScore": 2.2}]}, "affected": [{"source": "2499f714-1537-4658-8207-48ae4bb9eae9", "affectedData": [{"vendor": "curl", "product": "curl", "versions": [{"status": "affected", "version": "8.21.0", "versionType": "semver", "lessThanOrEqual": "8.21.0"}, {"status": "affected", "version": "8.20.0", "versionType": "semver", "lessThanOrEqual": "8.20.0"}, {"status": "affected", "version": "8.19.0", "versionType": "semver", "lessThanOrEqual": "8.19.0"}, {"status": "affected", "version": "8.18.0", "versionType": "semver", "lessThanOrEqual": "8.18.0"}, {"status": "affected", "version": "8.17.0", "versionType": "semver", "lessThanOrEqual": "8.17.0"}, {"status": "affected", "version": "8.16.0", "versionType": "semver", "lessThanOrEqual": "8.16.0"}, {"status": "affected", "version": "8.15.0", "versionType": "semver", "lessThanOrEqual": "8.15.0"}, {"status": "affected", "version": "8.14.1", "versionType": "semver", "lessThanOrEqual": "8.14.1"}, {"status": "affected", "version": "8.14.0", "versionType": "semver", "lessThanOrEqual": "8.14.0"}, {"status": "affected", "version": "8.13.0", "versionType": "semver", "lessThanOrEqual": "8.13.0"}, {"status": "affected", "version": "8.12.1", "versionType": "semver", "lessThanOrEqual": "8.12.1"}, {"status": "affected", "version": "8.12.0", "versionType": "semver", "lessThanOrEqual": "8.12.0"}, {"status": "affected", "version": "8.11.1", "versionType": "semver", "lessThanOrEqual": "8.11.1"}, {"status": "affected", "version": "8.11.0", "versionType": "semver", "lessThanOrEqual": "8.11.0"}, {"status": "affected", "version": "8.10.1", "versionType": "semver", "lessThanOrEqual": "8.10.1"}, {"status": "affected", "version": "8.10.0", "versionType": "semver", "lessThanOrEqual": "8.10.0"}, {"status": "affected", "version": "8.9.1", "versionType": "semver", "lessThanOrEqual": "8.9.1"}, {"status": "affected", "version": "8.9.0", "versionType": "semver", "lessThanOrEqual": "8.9.0"}, {"status": "affected", "version": "8.8.0", "versionType": "semver", "lessThanOrEqual": "8.8.0"}, {"status": "affected", "version": "8.7.1", "versionType": "semver", "lessThanOrEqual": "8.7.1"}, {"status": "affected", "version": "8.7.0", "versionType": "semver", "lessThanOrEqual": "8.7.0"}, {"status": "affected", "version": "8.6.0", "versionType": "semver", "lessThanOrEqual": "8.6.0"}, {"status": "affected", "version": "8.5.0", "versionType": "semver", "lessThanOrEqual": "8.5.0"}, {"status": "affected", "version": "8.4.0", "versionType": "semver", "lessThanOrEqual": "8.4.0"}, {"status": "affected", "version": "8.3.0", "versionType": "semver", "lessThanOrEqual": "8.3.0"}, {"status": "affected", "version": "8.2.1", "versionType": "semver", "lessThanOrEqual": "8.2.1"}, {"status": "affected", "version": "8.2.0", "versionType": "semver", "lessThanOrEqual": "8.2.0"}, {"status": "affected", "version": "8.1.2", "versionType": "semver", "lessThanOrEqual": "8.1.2"}, {"status": "affected", "version": "8.1.1", "versionType": "semver", "lessThanOrEqual": "8.1.1"}, {"status": "affected", "version": "8.1.0", "versionType": "semver", "lessThanOrEqual": "8.1.0"}, {"status": "affected", "version": "8.0.1", "versionType": "semver", "lessThanOrEqual": "8.0.1"}, {"status": "affected", "version": "8.0.0", "versionType": "semver", "lessThanOrEqual": "8.0.0"}, {"status": "affected", "version": "7.88.1", "versionType": "semver", "lessThanOrEqual": "7.88.1"}, {"status": "affected", "version": "7.88.0", "versionType": "semver", "lessThanOrEqual": "7.88.0"}, {"status": "affected", "version": "7.87.0", "versionType": "semver", "lessThanOrEqual": "7.87.0"}, {"status": "affected", "version": "7.86.0", "versionType": "semver", "lessThanOrEqual": "7.86.0"}, {"status": "affected", "version": "7.85.0", "versionType": "semver", "lessThanOrEqual": "7.85.0"}, {"status": "affected", "version": "7.84.0", "versionType": "semver", "lessThanOrEqual": "7.84.0"}, {"status": "affected", "version": "7.83.1", "versionType": "semver", "lessThanOrEqual": "7.83.1"}, {"status": "affected", "version": "7.83.0", "versionType": "semver", "lessThanOrEqual": "7.83.0"}, {"status": "affected", "version": "7.82.0", "versionType": "semver", "lessThanOrEqual": "7.82.0"}, {"status": "affected", "version": "7.81.0", "versionType": "semver", "lessThanOrEqual": "7.81.0"}, {"status": "affected", "version": "7.80.0", "versionType": "semver", "lessThanOrEqual": "7.80.0"}, {"status": "affected", "version": "7.79.1", "versionType": "semver", "lessThanOrEqual": "7.79.1"}, {"status": "affected", "version": "7.79.0", "versionType": "semver", "lessThanOrEqual": "7.79.0"}, {"status": "affected", "version": "7.78.0", "versionType": "semver", "lessThanOrEqual": "7.78.0"}, {"status": "affected", "version": "7.77.0", "versionType": "semver", "lessThanOrEqual": "7.77.0"}, {"status": "affected", "version": "7.76.1", "versionType": "semver", "lessThanOrEqual": "7.76.1"}, {"status": "affected", "version": "7.76.0", "versionType": "semver", "lessThanOrEqual": "7.76.0"}, {"status": "affected", "version": "7.75.0", "versionType": "semver", "lessThanOrEqual": "7.75.0"}], "defaultStatus": "unaffected"}]}], "published": "2026-10-20T20:17:25.223", "references": [{"url": "https://curl.se/docs/CVE-2026-86409.html", "source": "2499f714-1537-4658-8207-48ae4bb9eae9"}, {"url": "https://curl.se/docs/CVE-2026-86409.json", "source": "2499f714-1537-4658-8207-48ae4bb9eae9"}, {"url": "https://hackerone.com/reports/3973135", "source": "2499f714-1537-4658-8207-48ae4bb9eae9"}, {"url": "https://hackerone.com/reports/3973135", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}], "vulnStatus": "Awaiting Analysis", "weaknesses": [{"type": "Secondary", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "description": [{"lang": "en", "value": "CWE-201"}]}], "descriptions": [{"lang": "en", "value": "Setting `CURLOPT_AWS_SIGV4` to NULL but does not disable SigV4 authentication,\ncontrary to expectations and documentation. A subsequent transfer on the same\nhandle still sends an `Authorization: AWS4-HMAC-SHA256` header to whatever URL\nisset next, leaking state information."}], "lastModified": "2026-10-29T19:17:27.080", "sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9"}