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Noroxi
NVD / CVE Program· CNA curl

CVE-2026-1965: bad reuse of HTTP Negotiate connection

Noroxi assessment

Priority: Monitor (action score 26/100)

  • 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: 0.26% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: curl curl 8.14.2, 8.16.1, 8.19.0; azl3 curl 8.11.1-5 on Azure Linux 3.0 8.11.1-6; azl3 curl 8.11.1-6 on Azure Linux 3.0 8.11.1-6.

Low priority for now. Upgrade to curl curl 8.14.2, 8.16.1, 8.19.0; azl3 curl 8.11.1-5 on Azure Linux 3.0 8.11.1-6; azl3 curl 8.11.1-6 on Azure Linux 3.0 8.11.1-6 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

libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criterion must first be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. One underlying reason being that Negotiate sometimes authenticates *connections* and not *requests*, contrary to how HTTP is designed to work. An application that allows Negotiate authentication to a server (that responds wanting Negotiate) with `user1:password1` and then does another operation to the same server also using Negotiate but with `user2:password2` (while the previous connection is still alive) - the second request wrongly reused the same connection and since it then sees that the Negotiate negotiation is already made, it sends the request over that connection thinking it uses the user2 credentials when it is in fact still using the connection authenticated for user1... The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`. Applications can disable libcurl's reuse of connections and thus mitigate this problem, by using one of the following libcurl options to alter how connections are or are not reused: `CURLOPT_FRESH_CONNECT`, `CURLOPT_MAXCONNECTS` and `CURLMOPT_MAX_HOST_CONNECTIONS` (if using the curl_multi API).

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
Mar 11, 2026
Updated
Sep 15, 2026
EPSS
0.2% · 18th percentile

Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
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-2026-1965

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 curl7.10.6 and later · before 8.19.0

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

    • 8.18.0, 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, 8.10.1 … (+24)affected
    • 7.10.6 and later · before 8.14.2affected · semver
    • 8.15.0 and later · before 8.16.1affected · semver
    • 8.17.0 and later · before 8.19.0affected · semver
    • e56ae1426cb7a0a4a427cf8d6099a821fdaae428 and later · before f1a39f221d57354990e3eeeddc3404aede2aff70affected · git

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:9curlbefore 7.76.1-40.el9_8.57.76.1-40.el9_8.5
AlmaLinux:9curl-minimalbefore 7.76.1-40.el9_8.57.76.1-40.el9_8.5
AlmaLinux:9libcurlbefore 7.76.1-40.el9_8.57.76.1-40.el9_8.5
AlmaLinux:9libcurl-develbefore 7.76.1-40.el9_8.57.76.1-40.el9_8.5
AlmaLinux:9libcurl-minimalbefore 7.76.1-40.el9_8.57.76.1-40.el9_8.5
Alpine:v3.23curlfrom 7.10.6 · before 8.19.0-r08.19.0-r0
Debian:12curlfrom 0—
Debian:13curlbefore 8.14.1-2+deb13u48.14.1-2+deb13u4
Debian:14curlbefore 8.19.0~rc3-18.19.0~rc3-1
openSUSE:Leap 15.6curlbefore 8.14.1-150600.4.40.18.14.1-150600.4.40.1
openSUSE:Leap 16.0curlbefore 8.14.1-160000.5.18.14.1-160000.5.1
openSUSE:Tumbleweedcurlbefore 8.19.0-1.18.19.0-1.1
Red Hat:enterprise_linux_eus:10.0curlbefore 0:8.12.1-1.el10_0.100:8.12.1-1.el10_0.10
Red Hat:enterprise_linux_eus:10.0curl-debuginfobefore 0:8.12.1-1.el10_0.100:8.12.1-1.el10_0.10
Red Hat:enterprise_linux_eus:10.0curl-debugsourcebefore 0:8.12.1-1.el10_0.100:8.12.1-1.el10_0.10
Red Hat:enterprise_linux_eus:10.0libcurlbefore 0:8.12.1-1.el10_0.100:8.12.1-1.el10_0.10
Red Hat:enterprise_linux_eus:10.0libcurl-debuginfobefore 0:8.12.1-1.el10_0.100:8.12.1-1.el10_0.10
Red Hat:enterprise_linux_eus:10.0libcurl-develbefore 0:8.12.1-1.el10_0.100:8.12.1-1.el10_0.10
Red Hat:enterprise_linux_eus:10.0libcurl-minimalbefore 0:8.12.1-1.el10_0.100:8.12.1-1.el10_0.10
Red Hat:enterprise_linux_eus:10.0libcurl-minimal-debuginfobefore 0:8.12.1-1.el10_0.100:8.12.1-1.el10_0.10
Red Hat:enterprise_linux:10.2curlbefore 0:8.12.1-4.el10_2.30:8.12.1-4.el10_2.3
Red Hat:enterprise_linux:10.2curl-debuginfobefore 0:8.12.1-4.el10_2.30:8.12.1-4.el10_2.3
Red Hat:enterprise_linux:10.2curl-debugsourcebefore 0:8.12.1-4.el10_2.30:8.12.1-4.el10_2.3
Red Hat:enterprise_linux:10.2libcurlbefore 0:8.12.1-4.el10_2.30:8.12.1-4.el10_2.3

+36

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-2025-15079Jan 8, 2026 · libssh global known_hosts override
    21Monitor
  • ← EarlierCVE-2025-15224Jan 8, 2026 · libssh key passphrase bypass without agent set
    12Monitor
  • Later →CVE-2026-3783Mar 11, 2026 · token leak with redirect and netrc
    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 curl8.14.2Vendor (CNA)
curl curl8.16.1Vendor (CNA)
curl curl8.19.0Vendor (CNA)
curl curlf1a39f221d57354990e3eeeddc3404aede2aff70Vendor (CNA)
azl3 curl 8.11.1-5 on Azure Linux 3.08.11.1-6 · CBL-Mariner ReleasesMicrosoft (MSRC)
azl3 curl 8.11.1-6 on Azure Linux 3.08.11.1-6 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 curl 8.8.0-8 on CBL Mariner 2.08.8.0-9 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 curl 8.8.0-8 on CBL-Mariner 2.08.8.0-9 · Release NotesMicrosoft (MSRC)
almalinux:curl7.76.1-40.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:curl-minimal7.76.1-40.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:libcurl7.76.1-40.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:libcurl-devel7.76.1-40.el9_8.5 · AlmaLinux:9Package registry (OSV)
almalinux:libcurl-minimal7.76.1-40.el9_8.5 · AlmaLinux:9Package registry (OSV)
alpine:curl8.19.0-r0 · Alpine:v3.23Package registry (OSV)
debian:curl8.14.1-2+deb13u4 · Debian:13Package registry (OSV)
opensuse:curl8.14.1-150600.4.40.1 · openSUSE:Leap 15.6Package registry (OSV)
red hat:curl0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:curl-debuginfo0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:curl-debugsource0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:curl-minimal0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:curl-minimal-debuginfo0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libcurl0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:libcurl-debuginfo0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libcurl-devel0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libcurl-minimal0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:libcurl-minimal-debuginfo0:7.76.1-40.el9_8.5 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
rocky linux:curl0:7.76.1-40.el9_8.5 · Rocky Linux:9Package registry (OSV)
suse:curl8.14.1-150200.4.103.1 · SUSE:Linux Enterprise Micro 5.2Package registry (OSV)
suse:curl8.14.1-150600.4.40.1 · SUSE:Linux Enterprise Server 15 SP6-LTSSPackage registry (OSV)
suse:curl-mini8.14.1-160000.5.1 · 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.

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.

Variant candidates

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

  • CVE-2026-8932114 days apartincomplete mTLS config matching in conn reuse
    30Monitor
  • CVE-2026-37840 days apartwrong proxy connection reuse with credentials
    26Monitor
  • CVE-2026-554563 days apartwrong reuse of HTTP Negotiate connection
    26Monitor

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.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-305 · Authentication Bypass by Primary Weakness

CVSS vector

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

nvd-secondary

Attack context

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

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

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

References

Show all references (1 more)

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

All records