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CVE-2026-86409— stale SigV4 headers sent unintended

Quick assessment

Affected
curl curl
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

将 设置为 时，并不会如预期和文档所述那样禁用 SigV4 认证。在同一个句柄上进行的后续传输仍会向随后设置的任何 URL 发送 请求头，从而导致状态信息泄露。

AI Predicted 5.3 Difficulty: Moderate EPSS 1.10% · P66

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 50

VendorProduct Version RangeStatus
curl curl 8.21.0≤ 8.21.0 affected
8.20.0≤ 8.20.0 affected
8.19.0≤ 8.19.0 affected
8.18.0≤ 8.18.0 affected
8.17.0≤ 8.17.0 affected
8.16.0≤ 8.16.0 affected
8.15.0≤ 8.15.0 affected
8.14.1≤ 8.14.1 affected
… +42 more rows
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I. Basic Information for CVE-2026-86409

Vulnerability Information
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Vulnerability Title
stale SigV4 headers sent unintended
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
curl curl 8.21.0 ~ 8.21.0 -

II. Public POCs for CVE-2026-86409

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-86409

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Vendor Advisories for CVE-2026-86409 (1)

Vendor Pages for CVE-2026-86409 (1)

Other References for CVE-2026-86409 (1)

Same Patch Batch · curl · 2026-10-20 · 23 CVEs total

CVE-2026-92389 TFTP direction confusion
CVE-2026-107928 info leak uploading over WebSockets with GnuTLS
CVE-2026-107929 local interface connection reuse mixup
CVE-2026-94266 password leak in CURLINFO_EFFECTIVE_URL
CVE-2026-94265 Authorization: Negotiate sent to foreign origin
CVE-2026-86415 auto client cert connection reuse mixup
CVE-2026-86414 leaking host credentials to HTTP proxy
CVE-2026-92390 -J no-clobber guarantee bypassed with 103 early hints
CVE-2026-92387 never-ending loop via server response omission
CVE-2026-92388 FTP wildcard write callback mixup
CVE-2026-92386 server-set cookie aborts cookie jar load
CVE-2026-86413 Negotiate credentials sent to redirected origin
CVE-2026-92391 curl_mime_free stack overflow by recursion
CVE-2026-87865 knownhost callback mismatches key as missing
CVE-2026-87864 IMAP APPEND plus CRLF conversion command injection
CVE-2026-87863 HSTS response erases persisted entries
CVE-2026-87866 wolfSSL public-key pinning bypass
CVE-2026-87861 cross-origin reuse of a Negotiate connection
CVE-2026-87862 HSTS cache import drops longer-lived child
CVE-2026-86411 FTP connection reuse inherits client-certificate

Showing top 20 of 23 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: curl
Same vendor: curl