CVE-2026-107929
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libcurl Improper Connection Reuse via Interface Binding

Vulnerability report for CVE-2026-107929, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.

Publication date: 2026-10-20

Last updated on: 2026-10-30

Assigner: curl

Description

When `CURLOPT_INTERFACE` (or the command line tool's `--interface` option) is set with one of the documented prefixes (`if!`, `host!`, `ifhost!`), that binding is not part of the connection reuse key, so a later transfer asking for a different source can silently reuse an existing connection and go out from the earlier transfer's source address

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Meta Information

Published
2026-10-20
Last Modified
2026-10-30
Generated
2026-11-10
AI Q&A
2026-10-21
EPSS Evaluated
2026-11-08
NVD

Affected Vendors & Products

Showing 19 associated CPEs

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-488 The product does not sufficiently enforce boundaries between the states of different sessions, causing data to be provided to, or used by, the wrong session.

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Executive Summary

This vulnerability in curl occurs when the CURLOPT_INTERFACE option or --interface command line option is set with specific prefixes like if!, host!, or ifhost!. This causes the binding to not be included in the connection reuse key, allowing a later transfer with a different source to silently reuse an existing connection and send data from the earlier transfer's source address.

Detection Guidance

This vulnerability involves improper connection reuse in curl when specific interface prefixes are used. Detection requires checking curl versions and configurations using interface prefixes like if!, host!, or ifhost!. Use commands like 'curl --version' to check version and 'curl -V' to inspect supported features. Monitor network traffic for unexpected source address reuse during transfers.

Impact Analysis

This vulnerability could allow an attacker to send requests from an unintended source IP address, potentially bypassing network restrictions or obscuring the origin of malicious traffic. It may also lead to data leaks if sensitive information is transmitted from an unexpected source address.

Mitigation Strategies

Update curl to the latest version where this issue is patched. Avoid using the --interface option with prefixes like if!, host!, or ifhost! until the update is applied.

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