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curl EUVDEUVD-2026-29927

| CVE-2026-6253 MEDIUM
Insufficiently Protected Credentials (CWE-522)
2026-05-08
5.9
CVSS 3.1 · Vendor
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Identify curl client using proxy credentials
  2. Delivery
    Control or compromise redirect-serving endpoint
  3. Exploit
    Issue HTTP redirect targeting proxy endpoint
  4. Execution
    curl follows redirect forwarding proxy credentials
  5. Impact
    Attacker captures proxy authentication material

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V6 - Authentication Credential protection in transit/storage
Exploitation Conditions

Exploitation requires two concurrent conditions: (1) curl must be invoked with proxy authentication credentials configured - via the -U/--proxy-user flag, CURLOPT_PROXYUSERPWD in libcurl, the http_proxy environment variable with embedded credentials, or a .netrc entry - and (2) the target server must issue an HTTP redirect response whose Location header points to or resolves as a proxy endpoint. Exploitation is limited by AC:H (high attack complexity) and SSVC's 'Automatable: no,' meaning bulk unauthenticated scanning cannot trigger this at scale. The attacker must control or influence the redirect-issuing server and the victim must be using proxy credentials in that curl session. Curl instances not using proxy authentication are not affected regardless of redirect behavior.

Impact

CRITICAL DISCREPANCY requiring verification: the provided CVSS vector (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H) reports High availability impact with zero confidentiality impact, yet the vulnerability is titled 'proxy credentials leak,' carries CWE-522 (Insufficiently Protected Credentials), and is tagged 'Information Disclosure.' These signals are directly contradictory - a credential leak should register C:H, not A:H with C:N. Security teams must verify the CVSS vector against the vendor advisory at curl.se/docs/CVE-2026-6253.html before using this score for risk prioritization. If the confidentiality impact is actually high, the true CVSS score would be considerably higher than 5.9. Setting aside the vector conflict: EPSS at 0.02% (4th percentile) reflects very low broad exploitation probability, SSVC confirms a POC exists but rates it non-automatable with partial technical impact, and there is no CISA KEV listing - suggesting targeted rather than widespread exploitation risk. The AC:H (high attack complexity) is consistent with SSVC's 'Automatable: no,' indicating exploitation requires specific, non-trivial conditions rather than bulk scanning.

Exploit ScenarioDerived

A proof of concept exists per SSVC classification. An attacker who controls or compromises a web server visited by a curl client configured with proxy credentials crafts an HTTP redirect response pointing to a proxy endpoint; curl follows the redirect and includes the proxy authentication credentials in the outbound request, delivering them to the attacker-controlled destination. The high attack complexity (AC:H) means the attacker must engineer the precise redirect-to-proxy condition rather than simply serving a generic redirect, limiting opportunistic mass exploitation.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Jun 08, 2026

Proxy credentials in curl leak to unintended destinations when an HTTP redirect points to a proxy endpoint, exposing authentication material beyond its intended scope. This affects the curl library and CLI tool (haxx:curl) across a broad version range from 7.14.1 through 8.19.0, as enumerated in EUVD-2026-29927. A proof of concept exists per SSVC classification (Exploitation: poc), the vendor has issued a patch coordinated via oss-security and HackerOne report #3669637, and downstream distributors Red Hat (RHSA-2026:12916) and SUSE (multiple SU advisories) have released updates.

RemediationAI

The vendor has released a patch; consult the official advisory at https://curl.se/docs/CVE-2026-6253.html for the exact fixed version, as the precise patched release number is not independently confirmed from available input data - the highest enumerated affected version is 8.19.0. Red Hat users should apply RHSA-2026:12916 via standard yum/dnf update channels. SUSE users should apply SUSE-SU-2026:1717 or the applicable SU update for their SUSE/openSUSE release. As a compensating control where immediate upgrade is not possible: disable automatic redirect following in curl (--max-redirs 0 or CURLOPT_MAXREDIRS=0 in libcurl), accepting the trade-off that legitimate redirect flows will require manual handling. Alternatively, avoid embedding proxy credentials in curl invocations in environments where the target server is not fully trusted to control redirect destinations. Removing proxy credentials from the environment or .netrc where not strictly required eliminates the credential material available to leak.

Affected VersionsENISA

curl 7.15.2 ≤7.15.2
curl 8.13.0 ≤8.13.0
curl 7.55.1 ≤7.55.1
curl 7.50.2 ≤7.50.2
curl 8.19.0 ≤8.19.0
curl 7.53.0 ≤7.53.0
curl 8.7.0 ≤8.7.0
curl 7.42.0 ≤7.42.0
curl 7.19.3 ≤7.19.3
curl 7.19.2 ≤7.19.2
curl 7.65.0 ≤7.65.0
curl 7.16.3 ≤7.16.3
curl 7.30.0 ≤7.30.0
curl 7.15.3 ≤7.15.3
curl 7.15.5 ≤7.15.5
curl 7.25.0 ≤7.25.0
curl 7.15.0 ≤7.15.0
curl 7.64.1 ≤7.64.1
curl 7.17.1 ≤7.17.1
curl 8.6.0 ≤8.6.0
curl 7.31.0 ≤7.31.0
curl 7.76.1 ≤7.76.1
curl 7.71.1 ≤7.71.1
curl 8.11.0 ≤8.11.0
curl 7.24.0 ≤7.24.0
curl 7.52.1 ≤7.52.1
curl 8.3.0 ≤8.3.0
curl 7.49.0 ≤7.49.0
curl 7.58.0 ≤7.58.0
curl 7.16.0 ≤7.16.0
curl 7.21.1 ≤7.21.1
curl 7.71.0 ≤7.71.0
curl 7.42.1 ≤7.42.1
curl 7.73.0 ≤7.73.0
curl 7.21.3 ≤7.21.3
curl 7.50.0 ≤7.50.0
curl 7.19.0 ≤7.19.0
curl 8.4.0 ≤8.4.0
curl 7.62.0 ≤7.62.0
curl 7.67.0 ≤7.67.0
curl 7.50.1 ≤7.50.1
curl 7.86.0 ≤7.86.0
curl 7.64.0 ≤7.64.0
curl 7.17.0 ≤7.17.0
curl 7.79.0 ≤7.79.0
curl 7.14.1 ≤7.14.1
curl 7.16.4 ≤7.16.4
curl 7.48.0 ≤7.48.0
curl 7.21.0 ≤7.21.0
curl 7.21.5 ≤7.21.5
curl 8.2.0 ≤8.2.0
curl 8.18.0 ≤8.18.0
curl 7.82.0 ≤7.82.0
curl 7.85.0 ≤7.85.0
curl 7.45.0 ≤7.45.0
curl 7.46.0 ≤7.46.0
curl 7.19.5 ≤7.19.5
curl 7.61.0 ≤7.61.0
curl 7.50.3 ≤7.50.3
curl 7.66.0 ≤7.66.0
curl 7.15.1 ≤7.15.1
curl 7.88.1 ≤7.88.1
curl 7.29.0 ≤7.29.0
curl 7.65.1 ≤7.65.1
curl 7.34.0 ≤7.34.0
curl 7.51.0 ≤7.51.0
curl 7.72.0 ≤7.72.0
curl 7.68.0 ≤7.68.0
curl 7.56.0 ≤7.56.0
curl 8.5.0 ≤8.5.0
curl 8.1.1 ≤8.1.1
curl 7.80.0 ≤7.80.0
curl 7.28.1 ≤7.28.1
curl 8.9.0 ≤8.9.0
curl 7.19.6 ≤7.19.6
curl 8.8.0 ≤8.8.0
curl 7.37.0 ≤7.37.0
curl 8.17.0 ≤8.17.0
curl 7.61.1 ≤7.61.1
curl 7.56.1 ≤7.56.1
curl 7.65.2 ≤7.65.2
curl 7.37.1 ≤7.37.1
curl 7.55.0 ≤7.55.0
curl 7.78.0 ≤7.78.0
curl 7.54.0 ≤7.54.0
curl 7.65.3 ≤7.65.3
curl 7.21.4 ≤7.21.4
curl 8.1.0 ≤8.1.0
curl 7.32.0 ≤7.32.0
curl 7.70.0 ≤7.70.0
curl 7.23.1 ≤7.23.1
curl 7.22.0 ≤7.22.0
curl 7.16.2 ≤7.16.2
curl 8.1.2 ≤8.1.2
curl 7.87.0 ≤7.87.0
curl 7.33.0 ≤7.33.0
curl 7.59.0 ≤7.59.0
curl 7.19.7 ≤7.19.7
curl 7.76.0 ≤7.76.0
curl 8.12.1 ≤8.12.1
curl 7.21.6 ≤7.21.6
curl 7.18.0 ≤7.18.0
curl 8.11.1 ≤8.11.1
curl 8.9.1 ≤8.9.1
curl 8.0.1 ≤8.0.1
curl 7.57.0 ≤7.57.0
curl 8.10.1 ≤8.10.1
curl 7.20.1 ≤7.20.1
curl 7.28.0 ≤7.28.0
curl 8.14.0 ≤8.14.0
curl 7.43.0 ≤7.43.0
curl 8.7.1 ≤8.7.1
curl 7.60.0 ≤7.60.0
curl 7.54.1 ≤7.54.1
curl 8.15.0 ≤8.15.0
curl 7.47.1 ≤7.47.1
curl 8.14.1 ≤8.14.1
curl 7.84.0 ≤7.84.0
curl 7.41.0 ≤7.41.0
curl 7.69.0 ≤7.69.0
curl 7.19.1 ≤7.19.1
curl 8.16.0 ≤8.16.0
curl 7.52.0 ≤7.52.0
curl 7.53.1 ≤7.53.1
curl 8.0.0 ≤8.0.0
curl 8.2.1 ≤8.2.1
curl 7.44.0 ≤7.44.0
curl 7.26.0 ≤7.26.0
curl 7.35.0 ≤7.35.0
curl 7.79.1 ≤7.79.1
curl 8.12.0 ≤8.12.0
curl 7.47.0 ≤7.47.0
curl 7.36.0 ≤7.36.0
curl 7.88.0 ≤7.88.0
curl 7.39.0 ≤7.39.0
curl 7.23.0 ≤7.23.0
curl 7.38.0 ≤7.38.0
curl 7.75.0 ≤7.75.0
curl 7.19.4 ≤7.19.4
curl 7.21.7 ≤7.21.7
curl 7.69.1 ≤7.69.1
curl 7.40.0 ≤7.40.0
curl 7.18.1 ≤7.18.1
curl 7.18.2 ≤7.18.2
curl 7.21.2 ≤7.21.2
curl 7.49.1 ≤7.49.1
curl 7.20.0 ≤7.20.0
curl 7.83.0 ≤7.83.0
curl 7.63.0 ≤7.63.0
curl 7.81.0 ≤7.81.0
curl 7.15.4 ≤7.15.4
curl 7.77.0 ≤7.77.0
curl 7.27.0 ≤7.27.0
curl 7.16.1 ≤7.16.1
curl 8.10.0 ≤8.10.0
curl 7.74.0 ≤7.74.0
curl 7.83.1 ≤7.83.1

Affected Packages

euvd curl no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

curl (cpe:2.3:a:haxx:curl) is a ubiquitous open-source data transfer library and command-line tool implementing HTTP, HTTPS, FTP, SFTP, and numerous other protocols. The root cause is classified as CWE-522 (Insufficiently Protected Credentials): curl fails to withhold proxy authentication credentials when following an HTTP redirect whose destination URL itself resolves to or points at a proxy. The credential material - intended only for the proxy authentication handshake - is forwarded in the redirect-following request, where it may reach an attacker-controlled or unintended endpoint. This class of vulnerability is a connection-reuse or request-forwarding logic flaw, consistent with the coordinated curl advisory batch also addressing SMB connection reuse (CVE-2026-5773) and netrc credential leaks (CVE-2026-6429) announced the same day.

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Severity by source

Vendor (CNA) PRIMARY 5.9 MEDIUM
AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
SUSE MEDIUM
Red Hat 5.3 MEDIUM

Primary rating from Vendor (CNA).

CVSS VectorVendor

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

Lifecycle Timeline

3
CVSS changed
May 13, 2026 - 18:22 NVD
5.9 (MEDIUM)
CVE Published
May 08, 2026 - 06:45 nvd
UNKNOWN (no severity yet)
CVE Published
May 08, 2026 - 06:45 nvd
MEDIUM 5.9

Description PRE-NVD

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

Threat Intelligence Overview

EPSS Score
0.0%
Top 96% exploitable
Social Media
4
Sightings
Data Quality
7 sources
Confidence: High

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
Poc
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

30
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +30
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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Vendor StatusVendor

SUSE

Severity: Medium
Product Status
Container suse/manager/4.3/proxy-httpd:4.3.17.9.76.18 Container suse/manager/4.3/proxy-salt-broker:4.3.17.9.66.20 Container suse/sle-micro-rancher/5.3:latest Container suse/sle-micro-rancher/5.4:5.4.4.5.106 Container suse/sle-micro/5.3/toolbox:16.3-6.11.222 Container suse/sle-micro/5.4/toolbox:16.3-5.19.222 Container suse/sle-micro/5.5/toolbox:16.3-3.12.133 Container suse/sle-micro/base-5.5:2.0.4-5.8.271 Image SLES15-SP4-BYOS Image SLES15-SP4-BYOS-Azure Image SLES15-SP4-BYOS-EC2 Image SLES15-SP4-BYOS-GCE Image SLES15-SP4-CHOST-BYOS Image SLES15-SP4-CHOST-BYOS-Aliyun Image SLES15-SP4-CHOST-BYOS-Azure Image SLES15-SP4-CHOST-BYOS-EC2 Image SLES15-SP4-CHOST-BYOS-GCE Image SLES15-SP4-CHOST-BYOS-SAP-CCloud Image SLES15-SP4-HPC-BYOS Image SLES15-SP4-HPC-BYOS-Azure Image SLES15-SP4-HPC-BYOS-EC2 Image SLES15-SP4-HPC-BYOS-GCE Image SLES15-SP4-HPC-EC2 Image SLES15-SP4-HPC-GCE Image SLES15-SP4-Hardened-BYOS Image SLES15-SP4-Hardened-BYOS-Azure Image SLES15-SP4-Hardened-BYOS-EC2 Image SLES15-SP4-Hardened-BYOS-GCE Image SLES15-SP4-SAP-BYOS Image SLES15-SP4-SAP-BYOS-Azure Image SLES15-SP4-SAP-BYOS-EC2 Image SLES15-SP4-SAP-BYOS-GCE Image SLES15-SP4-SAP-Hardened Image SLES15-SP4-SAP-Hardened-Azure Image SLES15-SP4-SAP-Hardened-BYOS Image SLES15-SP4-SAP-Hardened-BYOS-Azure Image SLES15-SP4-SAP-Hardened-BYOS-EC2 Image SLES15-SP4-SAP-Hardened-BYOS-GCE Image SLES15-SP4-SAP-Hardened-GCE Image SLES15-SP5-BYOS-Azure Image SLES15-SP5-BYOS-EC2 Image SLES15-SP5-BYOS-GCE Image SLES15-SP5-CHOST-BYOS-Aliyun Image SLES15-SP5-CHOST-BYOS-Azure Image SLES15-SP5-CHOST-BYOS-EC2 Image SLES15-SP5-CHOST-BYOS-GCE Image SLES15-SP5-CHOST-BYOS-GDC Image SLES15-SP5-CHOST-BYOS-SAP-CCloud Image SLES15-SP5-EC2 Image SLES15-SP5-GCE Image SLES15-SP5-HPC-BYOS-Azure Image SLES15-SP5-HPC-BYOS-EC2 Image SLES15-SP5-HPC-BYOS-GCE Image SLES15-SP5-Hardened-BYOS-Azure Image SLES15-SP5-Hardened-BYOS-EC2 Image SLES15-SP5-Hardened-BYOS-GCE Image SLES15-SP5-SAP-Azure-3P Image SLES15-SP5-SAP-BYOS-Azure Image SLES15-SP5-SAP-BYOS-EC2 Image SLES15-SP5-SAP-BYOS-GCE Image SLES15-SP5-SAP-Hardened-Azure Image SLES15-SP5-SAP-Hardened-BYOS-Azure Image SLES15-SP5-SAP-Hardened-BYOS-EC2 Image SLES15-SP5-SAP-Hardened-BYOS-GCE Image SLES15-SP5-SAP-Hardened-GCE Affected
Container suse/sl-micro/6.0/baremetal-os-container:2.1.3-6.172 Container suse/sl-micro/6.0/kvm-os-container:2.1.3-6.155 Container suse/sl-micro/6.0/rt-os-container:2.1.3-7.168 Affected
Container suse/sl-micro/6.0/base-os-container:2.1.3-7.139 Container suse/sl-micro/6.0/toolbox:13.2-9.105 Image SL-Micro Affected
Container suse/sl-micro/6.1/baremetal-os-container:2.2.1-7.102 Container suse/sl-micro/6.1/kvm-os-container:2.2.1-5.127 Container suse/sl-micro/6.1/rt-os-container:2.2.1-5.116 Affected
Container suse/sl-micro/6.1/base-os-container:2.2.1-5.126 Image SL-Micro-Azure Image SL-Micro-BYOS-Azure Image SL-Micro-BYOS-EC2 Image SL-Micro-BYOS-GCE Image SL-Micro-EC2 Image SUSE-Multi-Linux-Manager-Proxy-BYOS-Azure Image SUSE-Multi-Linux-Manager-Proxy-BYOS-EC2 Image SUSE-Multi-Linux-Manager-Proxy-BYOS-GCE Image SUSE-Multi-Linux-Manager-Server-Azure-llc Image SUSE-Multi-Linux-Manager-Server-Azure-ltd Image SUSE-Multi-Linux-Manager-Server-BYOS-Azure Image SUSE-Multi-Linux-Manager-Server-BYOS-EC2 Image SUSE-Multi-Linux-Manager-Server-BYOS-GCE Image SUSE-Multi-Linux-Manager-Server-EC2-llc Image SUSE-Multi-Linux-Manager-Server-EC2-ltd Affected

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