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curl libcurl CVE-2026-82209

| EUVDEUVD-2026-72153 HIGH
Insertion of Sensitive Information Into Sent Data (CWE-201)
2026-09-02 GHSA-3hpw-4mfr-9f85
Information Disclosure Red Hat Curl Haxx
High
Disputed · 8.2 Vendor
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Attack ChainAIDerived

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

  1. Recon
    Identify shared PSL domain co-tenant (e.g., github.io)
  2. Delivery
    Host malicious server under that PSL domain
  3. Exploit
    Victim's curl fetches attacker resource with cookies enabled
  4. Install
    Attacker server returns Set-Cookie scoped to PSL domain
  5. C2
    curl stores PSL-scoped supercookie
  6. Execute
    Victim curl connects to legitimate co-tenant service
  7. Impact
    Supercookie replayed to unintended target

Vulnerability Assessment

Weakness
CWE
CWE-201
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V14 - Data Protection Outbound data filtering
Exploitation Conditions

Cookie handling must be active in the curl invocation (via -b/-c, --cookie, --cookie-jar, or CURLOPT_COOKIEFILE in libcurl); curl does not store cookies by default, so default-configuration deployments are not affected. The victim must connect to an attacker-controlled server and subsequently to a separate service sharing the same PSL domain entry. This combination of conditions - non-default cookie storage plus specific PSL-domain co-tenancy - significantly limits realistic exploitation. The bug affects only curl/libcurl versions 8.14.0 through 8.21.0; older versions and 8.22.0+ are not vulnerable.
Impact

No CVSS score or vector is provided in the input data, so all severity assessment is independently derived. The vulnerability requires a multi-step attack chain: the victim must use curl with cookie handling enabled, connect to an attacker-controlled server that sets a PSL-scoped cookie, and subsequently connect to an unrelated service sharing the same PSL domain - an elevated attack complexity scenario. The impact is limited to cookies stored and replayed by curl; there is no code execution vector. Real-world severity is therefore moderate: environments where curl is used in scripts or CI pipelines that hit multiple services under shared cloud-hosted domains (e.g., *.amazonaws.com, *.github.io) face the highest risk. No exploitation probability data (EPSS) is available, KEV status is absent, and no POC has been identified, all of which suggest low immediate exploitation urgency. The fix is already available.
Exploit ScenarioDerived

An attacker operates a server at attacker.shared-psl-domain.example (e.g., a site on github.io or a cloud-hosted subdomain). When a victim's curl-based tool or script retrieves content from that server, the server responds with a Set-Cookie header scoped to the PSL domain (e.g., Domain=github.io). curl incorrectly stores this supercookie. On the victim's next curl request to a different legitimate service under the same PSL domain, the cookie is replayed - leaking it to the unintended target or enabling session fixation. No public POC exists, but the attack is straightforward to implement given knowledge of the flaw.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 02, 2026

curl and libcurl through version 8.21.0 incorrectly handle domain-scoped cookies for Public Suffix List (PSL) domains, permitting a malicious server to set cookies scoped to a PSL entry rather than rejecting them as standards require. This flaw enables cross-subdomain cookie propagation under shared public suffix registries (e.g., github.io, co.uk), potentially exposing session tokens or enabling session fixation against other services the victim connects to under the same PSL domain. No public exploit code exists and CISA KEV listing is absent; the vulnerability was fixed in curl 8.22.0 released September 2, 2026.

RemediationAI

Upgrade to curl 8.22.0, released September 2, 2026, which includes the fix for PSL domain cookie handling. The curl project advisory index at https://curl.se/docs/vuln-8.21.0.html provides full details and patch references. Operators who cannot upgrade immediately should disable cookie persistence in curl-based tooling by removing -b, -c, --cookie, and --cookie-jar options, eliminating the vulnerable code path entirely with no functional trade-off for non-session-dependent use cases. For libcurl consumers, calling curl_easy_setopt with CURLOPT_COOKIEFILE set to NULL disables the cookie engine. Rock-solid curl LTS customers should coordinate with https://rock-solid.curl.dev for backport availability.

Affected VersionsENISA

curl 7.49.1 ≤7.49.1
curl 8.1.2 ≤8.1.2
curl 7.81.0 ≤7.81.0
curl 7.50.1 ≤7.50.1
curl 7.78.0 ≤7.78.0
curl 8.1.0 ≤8.1.0
curl 7.71.1 ≤7.71.1
curl 7.53.1 ≤7.53.1
curl 7.69.1 ≤7.69.1
curl 8.10.1 ≤8.10.1
curl 7.67.0 ≤7.67.0
curl 7.83.0 ≤7.83.0
curl 7.66.0 ≤7.66.0
curl 8.20.0 ≤8.20.0
curl 7.79.0 ≤7.79.0
curl 7.65.1 ≤7.65.1
curl 7.50.3 ≤7.50.3
curl 8.21.0 ≤8.21.0
curl 7.47.0 ≤7.47.0
curl 8.3.0 ≤8.3.0
curl 7.84.0 ≤7.84.0
curl 7.59.0 ≤7.59.0
curl 8.18.0 ≤8.18.0
curl 7.71.0 ≤7.71.0
curl 7.65.3 ≤7.65.3
curl 7.60.0 ≤7.60.0
curl 8.0.0 ≤8.0.0
curl 8.0.1 ≤8.0.1
curl 7.82.0 ≤7.82.0
curl 7.64.1 ≤7.64.1
curl 8.4.0 ≤8.4.0
curl 8.13.0 ≤8.13.0
curl 7.76.1 ≤7.76.1
curl 8.9.1 ≤8.9.1
curl 7.61.0 ≤7.61.0
curl 7.61.1 ≤7.61.1
curl 8.7.0 ≤8.7.0
curl 7.49.0 ≤7.49.0
curl 8.14.1 ≤8.14.1
curl 7.57.0 ≤7.57.0
curl 7.88.1 ≤7.88.1
curl 7.64.0 ≤7.64.0
curl 7.56.1 ≤7.56.1
curl 8.12.0 ≤8.12.0
curl 8.19.0 ≤8.19.0
curl 8.5.0 ≤8.5.0
curl 8.7.1 ≤8.7.1
curl 7.88.0 ≤7.88.0
curl 8.10.0 ≤8.10.0
curl 7.85.0 ≤7.85.0
curl 8.11.0 ≤8.11.0
curl 7.50.0 ≤7.50.0
curl 7.65.2 ≤7.65.2
curl 7.54.0 ≤7.54.0
curl 8.11.1 ≤8.11.1
curl 7.86.0 ≤7.86.0
curl 8.8.0 ≤8.8.0
curl 8.9.0 ≤8.9.0
curl 8.2.1 ≤8.2.1
curl 7.51.0 ≤7.51.0
curl 7.55.1 ≤7.55.1
curl 7.80.0 ≤7.80.0
curl 7.47.1 ≤7.47.1
curl 7.52.0 ≤7.52.0
curl 7.74.0 ≤7.74.0
curl 7.46.0 ≤7.46.0
curl 8.16.0 ≤8.16.0
curl 7.68.0 ≤7.68.0
curl 7.72.0 ≤7.72.0
curl 7.52.1 ≤7.52.1
curl 8.17.0 ≤8.17.0
curl 8.15.0 ≤8.15.0
curl 7.77.0 ≤7.77.0
curl 7.63.0 ≤7.63.0
curl 7.79.1 ≤7.79.1
curl 8.6.0 ≤8.6.0
curl 7.83.1 ≤7.83.1
curl 7.55.0 ≤7.55.0
curl 7.50.2 ≤7.50.2
curl 7.75.0 ≤7.75.0
curl 7.69.0 ≤7.69.0
curl 7.48.0 ≤7.48.0
curl 7.70.0 ≤7.70.0
curl 8.1.1 ≤8.1.1
curl 7.87.0 ≤7.87.0
curl 7.65.0 ≤7.65.0
curl 8.14.0 ≤8.14.0
curl 7.54.1 ≤7.54.1
curl 8.2.0 ≤8.2.0
curl 7.58.0 ≤7.58.0
curl 7.76.0 ≤7.76.0
curl 8.12.1 ≤8.12.1
curl 7.62.0 ≤7.62.0
curl 7.53.0 ≤7.53.0
curl 7.73.0 ≤7.73.0
curl 7.56.0 ≤7.56.0

Affected Packages

euvd curl no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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Technical ContextAI · show details

curl and libcurl implement HTTP cookie handling per RFC 6265, which requires that cookies MUST NOT be set for domains that appear in the Public Suffix List (e.g., .co.uk, .github.io, .s3.amazonaws.com). The PSL defines registry-controlled domain boundaries so that independent tenants sharing a common registrable suffix cannot set supercookies that span one another's namespaces. curl maintains an internal PSL copy to enforce this boundary. The flaw - described as 'domain-scoped PSL domain cookie' - means curl fails to reject Set-Cookie headers whose Domain attribute resolves to a PSL entry, allowing a cookie to be stored and replayed against all hosts under that suffix. No CWE is provided in the input data; the closest applicable root cause is CWE-565 (Reliance on Cookies without Validation and Integrity) or CWE-20 (Improper Input Validation on cookie domain attribute). Affected CPE is not formally published in the input data, but the advisory context confirms libcurl/curl packages in the 8.x line through 8.21.0.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Sources disagree (Low–High)
Vendor (CNA) PRIMARY 8.2 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
vuln.today AI 4.2 MEDIUM

Network vector but high complexity (PSL co-tenancy + cookie-enabled curl required); no privilege needed by attacker; user must initiate request; limited C and I from cookie misrouting only.

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

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor

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

Lifecycle Timeline

2
CVSS changed
Sep 08, 2026 - 19:23 NVD
8.2 (HIGH)
CVE Published
Sep 02, 2026 - 10:57 oss-security
MEDIUM

Description PRE-NVD

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

Threat Intelligence Overview

EPSS Score
0.2%
Top 88% exploitable
Prevalence
Ubiquitous
curl/libcurl in 20+ billion installations worldwide
Data Quality
6 sources
Confidence: High
EUVD 🇯🇵JVN NVD CVE.org EPSS MSRC Vendor VulDB

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 HIGH
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
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· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact· derived
High

Priority Score

41
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +41
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

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

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Same weakness CWE-201 – Insertion of Sensitive Information Into Sent Data

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8.6
CVE-2025-60188 HIGH POC
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CVE-2025-58098 HIGH POC
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Same technique Information Disclosure

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CVE-2013-2251 CRITICAL POC
9.8
CVE-2017-5638 CRITICAL POC
9.8
CVE-2025-24813 CRITICAL POC
9.8
CVE-2025-68613 HIGH POC
8.8
CVE-2015-1701 HIGH POC
7.8
CVE-2017-0147 HIGH POC
7.5

Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
openSUSE Tumbleweed Fixed
SLES15-SP5-CHOST-BYOS-SAP-CCloud Affected
SLES15-SP6-CHOST-BYOS Affected
SLES15-SP6-CHOST-BYOS-Aliyun Affected
SLES15-SP6-CHOST-BYOS-Azure Affected

References

Advisories & patches
ADVISORY https://curl.se/docs/CVE-2026-80256.html ADVISORY https://curl.se/docs/vuln-8.21.0.html ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-82209 ADVISORY https://rock-solid.curl.dev ADVISORY https://seclists.org/oss-sec/2026/q3/637 ADVISORY https://ubuntu.com/security/notices/USN-8820-1 ADVISORY https://vuldb.com/vuln/399469 REF https://curl.se/docs/CVE-2026-82209.html REF https://curl.se/docs/CVE-2026-82209.json REF https://hackerone.com/reports/3972385

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