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NVD / CVE Program· CNA curl

CVE-2026-6276: stale custom cookie host causes cookie leak

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: 0.29% (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 3a19987a87f393d9394fe5acc7643f6c263c92db, 8.14.2, 8.16.1; azl3 cmake 3.30.3-13 on Azure Linux 3.0 3.30.3-14; azl3 curl 8.11.1-6 on Azure Linux 3.0 8.11.1-7.

Low priority for now. Upgrade to curl curl 3a19987a87f393d9394fe5acc7643f6c263c92db, 8.14.2, 8.16.1; azl3 cmake 3.30.3-13 on Azure Linux 3.0 3.30.3-14; azl3 curl 8.11.1-6 on Azure Linux 3.0 8.11.1-7 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

Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
May 13, 2026
Updated
Sep 15, 2026
EPSS
0.2% · 22th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

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.

Follow CVE-2026-6276

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

VendorProduct
haxxcurl

Affected versions

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

  • haxx curl7.71.0 and later · before 8.20.0

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

    • 8.19.0, 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, 8.11.0 … (+24)affected
    • 7.71.0 and later · before 8.14.2affected · semver
    • 8.15.0 and later · before 8.16.1affected · semver
    • 8.17.0 and later · before 8.20.0affected · semver
    • e15e51384a423be31318b3c9c7d612a1aae661fd and later · before 3a19987a87f393d9394fe5acc7643f6c263c92dbaffected · git

Package-level exposure

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

EcosystemPackageAffected rangeFix
Alpine:v3.21curlfrom 7.71.0 · before 8.14.1-r38.14.1-r3
Alpine:v3.22curlfrom 7.71.0 · before 8.14.1-r48.14.1-r4
Alpine:v3.23curlfrom 7.71.0 · before 8.20.0-r08.20.0-r0
Debian:12curlfrom 0—
Debian:13curlbefore 8.14.1-2+deb13u48.14.1-2+deb13u4
Debian:14curlbefore 8.20.0~rc3-18.20.0~rc3-1
openSUSE:Leap 16.0curlbefore 8.14.1-160000.6.18.14.1-160000.6.1
openSUSE:Tumbleweedcurlbefore 8.20.0-1.18.20.0-1.1
Red Hat:hummingbird:1curlbefore 0:8.20.0-0.1.hum10:8.20.0-0.1.hum1
Red Hat:hummingbird:1libcurlbefore 0:8.20.0-0.1.hum10:8.20.0-0.1.hum1
Red Hat:hummingbird:1libcurl-develbefore 0:8.20.0-0.1.hum10:8.20.0-0.1.hum1
Red Hat:hummingbird:1libcurl-minimalbefore 0:8.20.0-0.1.hum10:8.20.0-0.1.hum1
SUSE:Linux Enterprise Module for Basesystem 15 SP7curlbefore 8.14.1-150700.7.23.18.14.1-150700.7.23.1
SUSE:Linux Enterprise Server 16.0curl-minibefore 8.14.1-160000.6.18.14.1-160000.6.1
SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5curlbefore 8.0.1-11.123.18.0.1-11.123.1
SUSE:Linux Micro 6.2curlbefore 8.14.1-160000.6.18.14.1-160000.6.1

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-2026-5773May 13, 2026 · wrong reuse of SMB connection
    30Monitor
  • ← EarlierCVE-2026-6253May 13, 2026 · proxy credentials leak over redirect-to proxy
    23Monitor
  • Later →CVE-2026-6429May 13, 2026 · netrc credential leak with reused proxy connection
    21Monitor

Remediation

Which version to upgrade to

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

Product / packageFixed versionSource
curl curl3a19987a87f393d9394fe5acc7643f6c263c92dbVendor (CNA)
curl curl8.14.2Vendor (CNA)
curl curl8.16.1Vendor (CNA)
curl curl8.20.0Vendor (CNA)
azl3 cmake 3.30.3-13 on Azure Linux 3.03.30.3-14 · CBL-Mariner ReleasesMicrosoft (MSRC)
azl3 curl 8.11.1-6 on Azure Linux 3.08.11.1-7 · CBL-Mariner ReleasesMicrosoft (MSRC)
azl3 curl 8.11.1-7 on Azure Linux 3.08.11.1-7 · CBL-Mariner ReleasesMicrosoft (MSRC)
alpine:curl8.14.1-r3 · Alpine:v3.21Package registry (OSV)
alpine:curl8.20.0-r0 · Alpine:v3.23Package registry (OSV)
debian:curl8.14.1-2+deb13u4 · Debian:13Package registry (OSV)
opensuse:curl8.20.0-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:curl0:8.20.0-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:libcurl0:8.20.0-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:libcurl-devel0:8.20.0-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:libcurl-minimal0:8.20.0-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
suse:curl8.14.1-160000.6.1 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:curl-mini8.14.1-160000.6.1 · SUSE:Linux Enterprise Server 16.0Package 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.

No history yet (it accumulates with the daily EPSS job).

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.

Variant candidates

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

No nightly-computed relations.

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
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-346 · Origin Validation Error

CVSS vector

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

nvd-primary

Attack context

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

Change log

  1. Fix✗ → ✓

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

References

Show all references (2 more)

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

All records