curl: Improper Restriction of Communication Channel to Intended Endpoints
CVE-2026-13608 is a high-severity improper restriction of communication channel to intended endpoints vulnerability in curl, with a CVSS 3.1 base score of 7.4 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 8.14.2, 8.16.1, 8.20.1 as the first without the flaw, so updating curl to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.5% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update curl to 8.14.2 or 8.16.1 or 8.20.1 or 8.22.0, whichever matches your release line, or a later version.
- Read the advisory on curl.se for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Curl | curl | 7.82.0 up to, but not including, 8.14.2; 8.15.0 up to, but not including, 8.16.1; 8.17.0 up to, but not including, 8.20.1; 8.21.0 up to, but not including, 8.22.0; eeca818b1e8d1e61c2d4d833aed56ce4c510a9d4 up to, but not including, ea71c3b6b60e563651ea8596a975aef0c8199519; 8.21.0; 8.20.0; 8.19.0; and 32 more ranges | 8.14.2, 8.16.1, 8.20.1, 8.22.0, ea71c3b6b60e563651ea8596a975aef0c8199519 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by CISA (ADP).
Official description
A flaw in the libcurl SASL negotiation for LDAP authentication allows an incomplete handshake sequence to be misinterpreted as a successful cryptographic verification. An attacker executing a Man-in-the-Middle (MITM) attack can inject a premature or shortcut response that bypasses complete peer validation.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Restriction of Communication Channel to Intended Endpoints
The product establishes a communication channel to (or from) an endpoint for privileged or protected operations, but it does not properly ensure that it is communicating with the correct endpoint.
More Improper Restriction of Communication Channel to Intended Endpoints vulnerabilities (CWE-923)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Technical write-ups (may include proof of concept)
- hackerone.com/reports/3822248Exploit, Third Party Advisory
Other vulnerabilities in curl
- 7.5 High severity
- 9.1 Critical severity
- 7.5 High severity
- 7.5 High severity
- 8.1 High severity
- 9.1 Critical severity
Recent Improper Restriction of Communication Channel to Intended Endpoints vulnerabilities
- 10.0 Critical severity
- 7.3 High severity
- 7.5 High severity
- 7.3 High severity
- 7.5 High severity
- 9.6 Critical severity
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