Cyber Resilience

CVE-2026-6276

Haxx Curl 7.71.0 – 8.20.0

Public PoC
Published
13 May 2026
Modified
17 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0029 22th percentile
Risk Priority 56 floored blend · peak EPSS

Summary

CVE-2026-6276 is a high-severity Cleartext Transmission of Sensitive Information (CWE-319) vulnerability in Haxx Curl. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Network Sniffing (T1040); ranked at the 22th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SC-8 (Transmission Confidentiality and Integrity) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A04:2025 Cryptographic Failures

EU & UK References

Vulnerability Data

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…

more

and pass on cookies meant for the first host in the second request. Leak them.

CWE(s)
CWE-319

Related Threats

MITRE ATT&CK Enterprise Techniques

T1040 Network Sniffing Credential Access
Adversaries may passively sniff network traffic to capture information about an environment, including authentication material passed over the network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-4873Same product: Haxx Curl
CVE-2025-15224Same product: Haxx Curl
CVE-2026-7168Same product: Haxx Curl
CVE-2026-11856Same product: Haxx Curl
CVE-2026-8927Same product: Haxx Curl
CVE-2026-6253Same product: Haxx Curl
CVE-2026-8926Same product: Haxx Curl
CVE-2026-3783Same product: Haxx Curl
CVE-2026-9079Same product: Haxx Curl
CVE-2026-11586Same product: Haxx Curl

Affected Assets

haxx
curl
7.71.0 — 8.20.0

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SC-8 Transmission Confidentiality and Integrity good match

SC-8 directly requires protecting confidentiality of transmitted information, which structurally eliminates cleartext transmission of sensitive data.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.DS-02 full match
prevents

Encryption of data-in-transit directly prevents cleartext transmission while the control also addresses integrity and availability.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.21 Security of network services mostly match
prevents

Specifying encryption and other security technology for network services prevents transmission of sensitive information in cleartext over potentially untrusted channels.

A.5.14 Information transfer partial match
prevents

Mandating cryptographic protection and stronger authentication on public networks stops the transmission of plaintext sensitive information.

A.6.7 Remote working partial match
mitigates

Specifying communications-security requirements and secure remote-access methods (including encryption expectations) prevents the transmission of sensitive data in cleartext over home or public networks.

A.7.12 Cabling security partial match
mitigates

Armoured conduits, electromagnetic shielding and locked enclosures make passive eavesdropping on unencrypted traffic traversing the cables more difficult, mitigating exposure of sensitive data in transit.

References