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curl CVE-2026-8286

| EUVDEUVD-2026-41503 HIGH
Improper Certificate Validation (CWE-295)
8.1
CVSS 3.1 · Vendor
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Severity by source

Vendor (CNA) PRIMARY
8.1 HIGH
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
vuln.today AI
7.4 HIGH

AC:H because it needs a pre-existing live STARTTLS connection with a mismatched TLS config eligible for reuse; PR:N as no auth to the client is required; C:H/I:H from data over an improperly-secured channel, A:N.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
SUSE
7.4 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Red Hat
8.1 HIGH
qualitative

Primary rating from Vendor (CNA).

CVSS VectorVendor

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Lifecycle Timeline

5
Analysis Updated
Jul 06, 2026 - 18:41 vuln.today
v3 (cvss_changed)
Analysis Updated
Jul 06, 2026 - 18:41 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Jul 06, 2026 - 18:22 vuln.today
cvss_changed
CVSS changed
Jul 06, 2026 - 18:22 NVD
8.1 (HIGH)
Analysis Generated
Jun 24, 2026 - 18:30 vuln.today

Description PRE-NVD

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

AnalysisAI

Information disclosure and integrity exposure in curl/libcurl occurs when a new transfer that uses STARTTLS to upgrade a connection may reuse an already-established live connection whose TLS configuration does not match the requested one, so data intended for a strictly-configured secure channel can traverse a connection negotiated under different (potentially weaker or unverified) TLS settings. The flaw affects a very wide range of curl releases from 7.30.0 through 8.20.0 and is tagged as Information Disclosure with high confidentiality and integrity impact (CVSS 8.1). It is not listed in CISA KEV, EPSS is low (0.20%, 9th percentile), and no public exploit code is identified at time of analysis.

Technical ContextAI

curl/libcurl maintains a connection cache and aggressively reuses established connections across transfers to avoid re-handshaking. For protocols that use STARTTLS (e.g. SMTP, IMAP, POP3, FTP with explicit TLS), a plaintext connection is upgraded in place to TLS. This bug is in the connection-reuse matching logic: a subsequent transfer carrying a different TLS configuration (differing verification, certificate, pinning, cipher, or version options) is incorrectly matched to and reused on an existing live connection whose TLS parameters differ, when it should have opened a fresh connection instead. The root cause is a connection-reuse/context-confusion issue (no CWE assigned in the source data; conceptually related to improper certificate/authentication validation and reuse-matching, e.g. CWE-295/CWE-863). The CPE-equivalent affected identifiers span the entire curl 7.x and 8.x product line as enumerated by the ENISA EUVD record (EUVD-2026-41503).

RemediationAI

Patch available per vendor advisory: upgrade curl/libcurl to the fixed release published by the curl project (see https://curl.se/docs/CVE-2026-8286.html for the exact patched version; no specific fix version is included in the provided data, so confirm it there rather than assuming one). Distribution users should apply the vendor-packaged update, e.g. per Ubuntu USN-8487-1 at https://ubuntu.com/security/notices/USN-8487-1, and rebuild or restart applications that statically or dynamically link libcurl so the fixed library is actually loaded. Where immediate patching is not possible, compensating controls include disabling connection reuse so each transfer opens a fresh connection (CURLOPT_FORBID_REUSE / CURLOPT_FRESH_CONNECT in libcurl, or --no-keepalive at the tool level), and using separate curl/libcurl handles for transfers that require different TLS configurations so mismatched connections are never pooled together; the trade-off is loss of connection-reuse performance and added handshake overhead. Cross-referenced advisories in the same disclosure batch include curl CVE-2026-11564, CVE-2026-12064, and CVE-2026-9080, so review those together when scheduling the upgrade.

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SLES15-SP5-CHOST-BYOS-SAP-CCloud Affected
SLES15-SP6-CHOST-BYOS Affected
SLES15-SP6-CHOST-BYOS-Aliyun Affected
SLES15-SP6-CHOST-BYOS-Azure Affected
SLES15-SP6-CHOST-BYOS-EC2 Affected

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CVE-2026-8286 vulnerability details – vuln.today

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