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🛡️ CVE-2026-1965 on Alpine — curl

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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).

Distribution advisory

This page covers CVE-2026-1965 as tracked by Alpine, for the package curl. The fix is available in version 8.19.0-r0; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity high, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: None.

Weakness class

ALPINE-CVE-2026-1965 is classified as CWE-305: Authentication Bypass by Primary Weakness. The authentication algorithm is sound, but the implemented mechanism can be bypassed as the result of a separate weakness that is primary to the authentication error.

Affected software

ALPINE-CVE-2026-1965 is recorded against 1 package.

  • curl (from 7.10.6 up to 8.19.0-r0)

Timeline and source

Published on 11 March 2026 and last revised on 8 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security.alpinelinux.org (Advisory)

Other advisories for this package

curl has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-305: Authentication Bypass by Primary Weakness) in other software:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-03-11
Updated 2026-08-20
Modified 2026-07-08
Fix URL N/A

Affected Packages

Software From version Fixed in
curl 7.10.6 8.19.0-r0

Vulnerability Monitoring

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