How severe is CVE-2026-6276?

CVE-2026-6276 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-6276 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-6276?

CVE-2026-6276 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-6276?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-6276 have an EU (EUVD) identifier?

Yes. CVE-2026-6276 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29928.

When was CVE-2026-6276 published?

CVE-2026-6276 was published on 2026-05-13 and last updated on 2026-06-17.

CVE-2026-6276

CVE-2026-6276 is a high-severity vulnerability in Haxx Curl with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-319.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (21st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-29928
Weakness: CWE-319
Affected product: Haxx Curl
Published: 2026-05-13
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2026-6276?: 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.
How severe is CVE-2026-6276?: CVE-2026-6276 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-6276 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-6276?: CVE-2026-6276 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-6276?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-6276 have an EU (EUVD) identifier?: Yes. CVE-2026-6276 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29928.
When was CVE-2026-6276 published?: CVE-2026-6276 was published on 2026-05-13 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

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