Skip to main content

Curl CVE-2026-1965

MEDIUM
Authentication Bypass by Primary Weakness (CWE-305)
2026-03-11 2499f714-1537-4658-8207-48ae4bb9eae9
Information Disclosure Curl Haxx
6.5
CVSS 3.1 · Vendor: 2499f714-1537-4658-8207-48ae4bb9eae9
View

Vulnerability Assessment

Weakness
CWE
CWE-305
OWASP Top 10:2025
A07:2025 - Authentication Failures
ASVS 5.0
V6 - Authentication Primary weakness mitigation
Impact

CVSS 6.5 (MEDIUM). Attack vector: Network. Complexity: Low. Privileges required: Low. User interaction: None. Exploitation requires authentication.
Exploit ScenarioDerived

An attacker (requires authentication) could exploit this vulnerability to compromise the affected system.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.1% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAIv1 – Mar 12, 2026

libcurl incorrectly reuses authenticated connections when processing Negotiate authentication requests, allowing an attacker with valid credentials to access resources authenticated under different user accounts. An authenticated attacker can exploit this connection pooling logic error to bypass authentication checks by reusing an existing connection that was authenticated with different credentials. This affects libcurl implementations using Negotiate authentication where multiple users access the same server.

Earlier versions of this analysis (1)
v1 Mar 12, 2026 - 22:06 CVSS 6.5

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. [CVSS 6.5 MEDIUM]

RemediationAI

A vendor patch is available — apply it immediately. Restrict network access to the affected service where possible.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

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

Sign in to check
Technical ContextAI · show details

Affects Curl. 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 diff

Know when Curl gets its next vulnerability

  • Watch products and get an email when something new is published
  • Check this CVE against your own stack and servers
  • Exploit and PoC references, threat intelligence from 22 sources
Continue with Google Continue with GitHub

No credit card · 7-day full trial

Severity by source

Vendor (2499f714-1537-4658-8207-48ae4bb9eae9) PRIMARY 6.5 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
SUSE MEDIUM
Red Hat 6.8 MEDIUM

Primary rating from Vendor (2499f714-1537-4658-8207-48ae4bb9eae9).

CVSS VectorVendor: 2499f714-1537-4658-8207-48ae4bb9eae9

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

Lifecycle Timeline

2
Patch released
Mar 12, 2026 - 14:11 nvd
Patch available
CVE Published
Mar 11, 2026 - 11:15 nvd
MEDIUM 6.5

DescriptionCVE.org

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 just 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).

Executive ViewAI

Why It Matters

CVE-2026-1965 presents notable security risk rated CVSS 6.5. Exploitation could compromise the security of affected deployments. A patch is available and should be applied during regular vulnerability management.

Business Impact: Moderate
Compensating Controls

Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.

Threat Intelligence Overview

EPSS Score
0.1%
Top 82% exploitable
Data Quality
5 sources
Confidence: Medium
NVD CVE.org EPSS 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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.1%
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

Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No

Priority Score

32
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +32
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.

Affected Products (CPE)CVE.org

cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

Related Vulnerabilities in curl Connection Reuse and Token Leakage

View all 4
CVE-2026-3805 HIGH POC
7.5
CVE-2026-3783 MEDIUM POC
5.3
CVE-2026-3784 MEDIUM POC
6.5

More in Curl

View all
CVE-2021-22901 HIGH POC
8.1 Jun 11

curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when
CVE-2013-0249 HIGH POC
7.5 Mar 08

Stack-based buffer overflow in the Curl_sasl_create_digest_md5_message function in lib/curl_sasl.c in curl and libcurl 7
CVE-2015-3145 HIGH
7.5 Apr 24

The sanitize_cookie_path function in cURL and libcurl 7.31.0 through 7.41.0 does not properly calculate an index, which

CVE-2022-32206 MEDIUM POC
6.5 Jul 07

curl < 7.84.0 supports "chained" HTTP compression algorithms, meaning that a serverresponse can be compressed multiple t
CVE-2022-32207 CRITICAL POC
9.8 Jul 07

When curl < 7.84.0 saves cookies, alt-svc and hsts data to local files, it makes the operation atomic by finalizing the

CVE-2022-43551 HIGH POC
7.5 Dec 23

A vulnerability exists in curl <7.87.0 HSTS check that could be bypassed to trick it to keep using HTTP. Rated high seve
CVE-2022-32221 CRITICAL POC
9.8 Dec 05

When doing HTTP(S) transfers, libcurl might erroneously use the read callback (`CURLOPT_READFUNCTION`) to ask for data t
CVE-2018-0500 CRITICAL POC
9.8 Jul 11

Curl_smtp_escape_eob in lib/smtp.c in curl 7.54.1 to and including curl 7.60.0 has a heap-based buffer overflow that mig
CVE-2022-32205 MEDIUM POC
4.3 Jul 07

A malicious server can serve excessive amounts of `Set-Cookie:` headers in a HTTP response to curl and curl < 7.84.0 sto
CVE-2025-9086 HIGH POC
7.5 Sep 12

1. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack co
CVE-2023-23914 CRITICAL POC
9.1 Feb 23

A cleartext transmission of sensitive information vulnerability exists in curl <v7.88.0 that could cause HSTS functional
CVE-2023-27534 HIGH POC
8.8 Mar 30

A path traversal vulnerability exists in curl <8.0.0 SFTP implementation causes the tilde (~) character to be wrongly re

Same weakness CWE-305 – Authentication Bypass by Primary Weakness

View all
CVE-2025-31161 CRITICAL POC
9.8
CVE-2026-81578 HIGH POC
8.8
CVE-2024-50478 CRITICAL
9.8
CVE-2023-34124 CRITICAL POC
9.8
CVE-2026-25555 CRITICAL POC
9.3
CVE-2023-1307 CRITICAL POC
9.8
CVE-2023-0777 CRITICAL POC
9.8
CVE-2022-2651 CRITICAL POC
9.8

Same technique Information Disclosure

View all
CVE-2019-2725 CRITICAL POC
9.8
CVE-2021-34523 CRITICAL POC
9.0
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: Medium
Product Status
Container suse/ltss/sle12.5/sles12sp5:8.5.210 Affected
Container suse/manager/4.3/proxy-httpd:4.3.16.2.9.73.25 Container suse/manager/4.3/proxy-salt-broker:4.3.16.2.9.63.26 Container suse/sle-micro/base-5.5:2.0.4-5.8.252 Image SLES15-SP5-SAP-Azure-LI-BYOS Image SLES15-SP5-SAP-Azure-LI-BYOS-Production Image SLES15-SP5-SAP-Azure-VLI-BYOS Image SLES15-SP5-SAP-Azure-VLI-BYOS-Production Affected
Container suse/manager/5.0/x86_64/proxy-httpd:latest Container suse/manager/5.0/x86_64/proxy-salt-broker:latest Container suse/manager/5.0/x86_64/server:latest Affected
Container suse/manager/5.0/x86_64/server-hub-xmlrpc-api:latest Container suse/manager/5.0/x86_64/server-migration-14-16:latest Affected
Container suse/sl-micro/6.0/baremetal-os-container:2.1.3-6.140 Affected

References

Advisories & patches
PATCH https://curl.se/docs/CVE-2026-1965.html ADVISORY https://curl.se/docs/CVE-2026-1965.json ADVISORY https://ubuntu.com/security/notices/USN-8084-1 ADVISORY https://vuldb.com/?id.350373 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0879/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0885/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0903/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0911/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:0921/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20668/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20722/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20760/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20918/

Search Externally

GitHub PoC Exploit-DB PacketStorm Snyk Rapid7 Nuclei Templates Trickest PoC
Back

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy