CVE-2026-9545· NVD / CVE Program· CNA curl

exposing HTTP/3 early data

Noroxi assessment

Priority: Monitor (action score 30/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.40% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: curl curl 7b9613fa9b1a5e04301a3920eef58e8138dad05e, 8.14.2, 8.16.1.

Low priority for now. Upgrade to curl curl 7b9613fa9b1a5e04301a3920eef58e8138dad05e, 8.14.2, 8.16.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In this scenario, libcurl first uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate. When libcurl returns to the hostname the second time with a cached SSL session (`CURLOPT_SSL_SESSIONID_CACHE` is not disabled) and early data enabled (the `CURLSSLOPT_EARLYDATA` bit is set in `CURLOPT_SSL_OPTIONS`), libcurl might send off the second request's bytes on that new connection *before* enforcing the certificate verification failure. Potentially leaking sensitive information.

HighCVSS 7.5 · v3.1—No exploit Fix available

Published: Jul 3, 2026
Updated: Sep 15, 2026
EPSS: 0.4% · 33th percentile
CWE: CWE-200

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CISA SSVC decision

Exploitation: proof of concept
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
haxx	curl	cpe:2.3:a:haxx:curl

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

haxx curl8.11.0 and later · before 8.21.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (curl). Independent of NVD's CPE analysis and usually ahead of it.

curl curl
- 8.20.0, 8.19.0, 8.18.0, 8.17.0, 8.16.0, 8.15.0, 8.14.1, 8.14.0, 8.13.0, 8.12.1, 8.12.0, 8.11.1 … (+1)affected
- 8.11.0 and later · before 8.14.2affected · semver
- 8.15.0 and later · before 8.16.1affected · semver
- 8.17.0 and later · before 8.20.1affected · semver
- 962097b8dd44ed5b9e7984bc1cdffdbdd566857f and later · before 7b9613fa9b1a5e04301a3920eef58e8138dad05eaffected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Alpine:v3.23	curl	from 8.11.0 · before 8.22.0-r0	8.22.0-r0
Alpine:v3.24	curl	from 8.11.0 · before 8.21.0-r0	8.21.0-r0
Debian:13	curl	from 0	—
Debian:14	curl	before 8.21.0~rc2-1	8.21.0~rc2-1
openSUSE:Leap 16.0	curl	before 8.14.1-160000.8.1	8.14.1-160000.8.1
openSUSE:Tumbleweed	curl	before 8.21.0-1.1	8.21.0-1.1
Red Hat:hummingbird:1	curl	before 0:8.21.0-0.1.1.hum1	0:8.21.0-0.1.1.hum1
Red Hat:hummingbird:1	libcurl	before 0:8.21.0-0.1.1.hum1	0:8.21.0-0.1.1.hum1
Red Hat:hummingbird:1	libcurl-devel	before 0:8.21.0-0.1.1.hum1	0:8.21.0-0.1.1.hum1
Red Hat:hummingbird:1	libcurl-minimal	before 0:8.21.0-0.1.1.hum1	0:8.21.0-0.1.1.hum1
SUSE:Linux Enterprise Installer Updates 15 SP4	curl	before 8.14.1-150400.5.86.1	8.14.1-150400.5.86.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7	curl	before 8.14.1-150700.7.20.1	8.14.1-150700.7.20.1
SUSE:Linux Enterprise Server 15 SP6-LTSS	curl	before 8.14.1-150600.4.46.1	8.14.1-150600.4.46.1
SUSE:Linux Enterprise Server 16.0	curl-mini	before 8.14.1-160000.8.1	8.14.1-160000.8.1
SUSE:Linux Micro 6.0	curl	before 8.14.1-7.1	8.14.1-7.1
SUSE:Linux Micro 6.1	curl	before 8.14.1-slfo.1.1_8.1	8.14.1-slfo.1.1_8.1
SUSE:Linux Micro 6.2	curl	before 8.14.1-160000.8.1	8.14.1-160000.8.1

Same product

haxx: all records

Other highest-scoring records for the same primary product.

CVE-2021-22901curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session t
51Plan
CVE-2023-38039When curl retrieves an HTTP response, it stores the incoming headers so that they can be accessed later via the libcurl headers API.
47Plan
CVE-2024-2398HTTP/2 push headers memory-leak
45Plan

Published before and after this one in the same product

← EarlierCVE-2026-9079Jul 3, 2026 · stale proxy password leak
39Monitor
← EarlierCVE-2026-9080Jul 3, 2026 · UAF after pause in socket callback
29Monitor
Later →CVE-2026-9546Jul 3, 2026 · A vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared.
30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
curl curl	7b9613fa9b1a5e04301a3920eef58e8138dad05e	Vendor (CNA)
curl curl	8.14.2	Vendor (CNA)
curl curl	8.16.1	Vendor (CNA)
curl curl	8.20.1	Vendor (CNA)
alpine:curl	8.22.0-r0 · Alpine:v3.23	Package registry (OSV)
debian:curl	8.21.0~rc2-1 · Debian:14	Package registry (OSV)
opensuse:curl	8.21.0-1.1 · openSUSE:Tumbleweed	Package registry (OSV)
red hat:curl	0:8.21.0-0.1.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:libcurl	0:8.21.0-0.1.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:libcurl-devel	0:8.21.0-0.1.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:libcurl-minimal	0:8.21.0-0.1.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
suse:curl	8.14.1-160000.8.1 · SUSE:Linux Micro 6.2	Package registry (OSV)
suse:curl-mini	8.14.1-160000.8.1 · SUSE:Linux Enterprise Server 16.0	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Stefan Eissingremediation developer
Eunsoo Kim (Autonomous Code Security team at Microsoft)finder

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-95460 days apartA vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared.
30Monitor
CVE-2026-642951 days apartnetrc credential leak with reused proxy connection
21Monitor
CVE-2025-0167513 days apartnetrc and default credential leak
13Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: none
Availability: none

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: None
Availability impact: None

Weakness class (CWE)

CWE-200 · Exposure of Sensitive Information to an Unauthorized Actor

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

nvd-secondary

Root cause

The extension requests broader permissions than its function needs and sends the data it collects out for purposes beyond its stated function.

The bug in code

The whole CWE-200 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

json

1{
2  "permissions": ["tabs", "<all_urls>"],
3  "background": { "service_worker": "analytics.js" }
4}

Fixed

json

1{
2  "permissions": ["activeTab"],
3  "host_permissions": ["https://yildiz.example/*"]
4}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Change log

Fix✗ → ✓Sep 28, 2026, 9:54 PM UTC

For records you follow, these changes also arrive as notifications. →

References

curl.se/docs/CVE-2026-9545.html

Show all references (1 more)

curl.se/docs/CVE-2026-9545.json

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records