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curl CVE-2026-80255

CRITICAL
2026-09-02
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vuln.today AI
3.7 LOW

Network vector because cookie is exposed over HTTP; AC:H because attacker needs a tab-crafted Set-Cookie plus HTTP-observable subsequent request; C:L for cookie-value disclosure only.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
4.0 AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Lifecycle Timeline

2
Analysis Generated
Sep 02, 2026 - 12:21 vuln.today
CVE Published
Sep 02, 2026 - 10:57 oss-security
CRITICAL

Description PRE-NVD

Disclosed via oss-security. NVD scoring and full description are pending.

AnalysisAI

Secure cookie attribute bypass in curl allows the Secure flag on HTTP cookies to be circumvented when a tab character is present in a Set-Cookie header, causing curl to potentially transmit cookies over unencrypted HTTP connections that should be restricted to HTTPS only. The flaw affects the cookie parsing logic in curl/libcurl and is fixed in curl 8.22.0, released September 2, 2026. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires two concurrent conditions: (1) the victim application uses curl or libcurl to communicate with a server that issues a `Set-Cookie` header containing a tab character positioned to disrupt `Secure` attribute parsing - this can be attacker-controlled or a legitimate server whose response is tampered with in transit; and (2) curl subsequently makes at least one HTTP (non-TLS) request to a domain in scope for the affected cookie, allowing a network observer to intercept the transmission. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment No CVSS vector was provided in the input data, so all metric assessments below are independently derived. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade to curl 8.22.0 (released September 2, 2026), which contains the fix for CVE-2026-80255 alongside patches for eight other vulnerabilities in the same release. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, identify all instances of curl and libcurl across the organization, including development environments, production systems, containerized services, API clients, embedded tools, and CI/CD infrastructure; prioritize systems handling authentication or sensitive data. …

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CVE-2026-80255 vulnerability details – vuln.today

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