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CVE-2026-6276

HIGH 7.5 ALL-YEARS

Published 2026-05-13 · Last modified 2026-09-15 · curl · NVD: Modified

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

ELEVATED IMPACT

Severe if exploited (CVSS 7.5), but no confirmed exploitation. Patch on a normal cadence.

Exploitation likelihood

0.3%chance of exploitation in 30 days · 22nd percentile

○ In CISA KEV○ Catalogued PoC◆ SSVC: exploitation poc, automatable yes

Impact if exploited

7.5CVSS 3.1 · HIGH · ADP

  • ConfidentialityNone
  • IntegrityNone
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

Search for new PoCs

Search GitHub now — results may be empty or unverified.

Tracked sources are checked weekly for the full archive, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Data snapshot:

Affected

Vendors Curl Haxx

Products Curl

Weakness (CWE)

  • CWE-346: Origin Validation Error
  • CWE-319: Cleartext Transmission of Sensitive Information

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References and research data (JSON)

Vendor product assessments

Showing 32 of 102 vendor product statements; 70 omitted. Read the full vendor advisory.

  • curl-0:8.20.0-0.1.hum1@aarch64 as a component of Red Hat Hardened Images · fixed

    Vendor assessment for this product only.

    pkg:rpm/redhat/[email protected]?arch=aarch64&distro=hummingbird-20251124&repository_id=public-hummingbird-aarch64-rpms

    • vendor fix: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/ Vendor guidance
    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • curl-0:8.20.0-0.1.hum1@src as a component of Red Hat Hardened Images · fixed

    Vendor assessment for this product only.

    pkg:rpm/redhat/[email protected]?arch=src&distro=hummingbird-20251124&repository_id=public-hummingbird-source-rpms

    • vendor fix: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/ Vendor guidance
    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • curl-0:8.20.0-0.1.hum1@x86_64 as a component of Red Hat Hardened Images · fixed

    Vendor assessment for this product only.

    pkg:rpm/redhat/[email protected]?arch=x86_64&distro=hummingbird-20251124&repository_id=public-hummingbird-x86_64-rpms

    • vendor fix: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/ Vendor guidance
    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • build-of-trustee/trustee-rhel9 as a component of Confidential Compute Attestation · known affected

    Vendor assessment for this product only.

    pkg:oci/trustee-rhel9?repository_url=registry.redhat.io/build-of-trustee/trustee-rhel9

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • openshift-sandboxed-containers/osc-podvm-builder-rhel9 as a component of Confidential Compute Attestation · known affected

    Vendor assessment for this product only.

    pkg:oci/osc-podvm-builder-rhel9?repository_url=registry.redhat.io/openshift-sandboxed-containers/osc-podvm-builder-rhel9

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • openshift-logging/cluster-logging-operator-bundle as a component of Logging Subsystem for Red Hat OpenShift · known affected

    Vendor assessment for this product only.

    pkg:oci/cluster-logging-operator-bundle?repository_url=registry.redhat.io/openshift-logging/cluster-logging-operator-bundle

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • openshift-logging/fluentd-rhel9 as a component of Logging Subsystem for Red Hat OpenShift · known affected

    Vendor assessment for this product only.

    pkg:oci/fluentd-rhel9?repository_url=registry.redhat.io/openshift-logging/fluentd-rhel9

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • curl as a component of Red Hat Enterprise Linux 10 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/curl

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Affected
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • libcurl-devel as a component of Red Hat Enterprise Linux 10 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/libcurl-devel

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Affected
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • curl as a component of Red Hat Enterprise Linux 6 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/curl

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • libcurl-devel as a component of Red Hat Enterprise Linux 6 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/libcurl-devel

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • libcurl as a component of Red Hat Enterprise Linux 7 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/libcurl

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • curl.src as a component of Red Hat Enterprise Linux 8 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/curl?arch=src

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • libcurl-minimal as a component of Red Hat Enterprise Linux 8 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/libcurl-minimal

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • libcurl as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/libcurl

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Affected
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • snphost.src as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/snphost?arch=src

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Affected
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • openshift/ose-rhel-coreos-8 as a component of Red Hat OpenShift Container Platform 4 · known affected

    Vendor assessment for this product only.

    pkg:oci/ose-rhel-coreos-8?repository_url=registry.redhat.io/openshift/ose-rhel-coreos-8

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rhtpa/rhtpa-trustification-service-rhel9 as a component of Red Hat Trusted Profile Analyzer · known affected

    Vendor assessment for this product only.

    pkg:oci/rhtpa-trustification-service-rhel9?repository_url=registry.redhat.io/rhtpa/rhtpa-trustification-service-rhel9

    • workaround: To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
    • none available: Fix deferred
    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • cargo as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: component not present

    pkg:rpm/redhat/cargo

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rust-debugger-common as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: component not present

    pkg:rpm/redhat/rust-debugger-common

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rust-src as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: component not present

    pkg:rpm/redhat/rust-src

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rust-std-static-wasm32-wasip1 as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: component not present

    pkg:rpm/redhat/rust-std-static-wasm32-wasip1

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rust.src as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: component not present

    pkg:rpm/redhat/rust?arch=src

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • s390utils-cmsfs-fuse as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/s390utils-cmsfs-fuse

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • s390utils-devel as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/s390utils-devel

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • s390utils-se-data as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/s390utils-se-data

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • trustee-guest-components.src as a component of Red Hat Enterprise Linux 10 · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/trustee-guest-components?arch=src

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rust as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: component not present

    pkg:rpm/redhat/rust

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rust-doc as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: component not present

    pkg:rpm/redhat/rust-doc

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rust-std-static as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: component not present

    pkg:rpm/redhat/rust-std-static

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rust-toolset as a component of Red Hat Enterprise Linux 9 · known not affected

    Vendor assessment for this product only.

    Reason: component not present

    pkg:rpm/redhat/rust-toolset

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00
  • rust.src as a component of Red Hat Hardened Images · known not affected

    Vendor assessment for this product only.

    Reason: vulnerable code not present

    pkg:rpm/redhat/rust?arch=src

    Red Hat · CVE-2026-6276 · Updated 2026-09-22T12:22:42+00:00

Known Affected Software Configurations

VendorProductVersion range
HaxxCurl≥ 7.71.0 and < 8.20.0

All CVSS metrics

  • HIGH 7.5 v3.1 · ADP Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  • HIGH 7.5 v3.1 · NVD Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Exploit-tagged references (not proof of a PoC)

Patches & mitigations

Advisories

Technical & other

Sources: NVD · CVE.org · All sources and attribution · EPSS