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Findings

CVE-2026-6276

Using libcurl, when a custom header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom head…

Published May 13, 2026 · corrected/updated Sep 15, 2026 · haxx curl · evidence confidence medium

Using libcurl, when a custom header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2026-6276 is a high public vulnerability record for haxx curl. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether haxx curl is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: haxx/curl. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: CVSS 7.5. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-319, CWE-346. Sources contributing to this record: cve_org, nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in the CISA KEV catalog.

  • Patch and remediation

    No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 13, 2026 · NIST NVD

    Detected

    Using libcurl, when a custom header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

  2. Sep 15, 2026 · NIST NVD

    Updated

    Using libcurl, when a custom header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

Affected

  • cpe haxx/curlversion unspecified

Sources

  • CVE.orgVulnerability recordCVE-2026-6276

    Official CVE identifier

    cve.org
  • NIST NVDVulnerability recordCVE-2026-6276

    Using libcurl, when a custom header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom header set, the second request would use stale information and pass on cookies meant for the first ho

    nvd.nist.gov

References