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CVE-2026-8927

Haxx Curl authentication bypass

9.1 CRITICALPublic exploitEPSS 0.50%
  1. Published3 Jul 2026

Description

When reusing a libcurl handle for sequential transfers driven by environment-variable proxy configuration, libcurl fails to clear the proxy authentication state between requests. Specifically, if the initial transfer authenticates against `proxyA` using Digest auth, a subsequent transfer routed through `proxyB` erroneously leaks the `Proxy-Authorization:` header intended solely for `proxyA`.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Haxx Curl≥ 7.12.0 < 8.21.0

Remediation

Fixed in
Haxx Curl≥ 8.21.0

References

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Frequently asked

Is CVE-2026-8927 being actively exploited?

CVE-2026-8927 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.50%.

How severe is CVE-2026-8927?

CVE-2026-8927 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.50% probability of exploitation.

Which products are affected by CVE-2026-8927?

Affected products include Haxx Curl.

How do I fix CVE-2026-8927?

Upgrade affected software to a fixed version, for example Haxx Curl 8.21.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.