CVE-2026-19931: curl — Exploit & Fix

Description

A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication, when the initial request is done using empty credentials. This can make user B's request get sent over user A's previously authenticated connection.

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CVSS v3.1 Score

9.8

CRITICAL

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

EPSS — Exploit Prediction

0.0116

Probability of exploitation

0.66%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-488 CWE-488

Affected Products

Vendor	Product	Versions
haxx	curl	7.64.1 — 8.22.0

References

Advisories & Patches

https://curl.se/docs/CVE-2026-19931.html https://curl.se/docs/CVE-2026-19931.json

Exploits

https://hackerone.com/reports/3923520 https://hackerone.com/reports/3923520

Frequently Asked Questions

What is CVE-2026-19931? +

A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication, when the initial request is done using empty credentials. This can make user B's request get sent over user A's previously authenticated connection. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-19931? +

CVE-2026-19931 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0116, placing it in the 1th percentile for exploitation probability.

What products are affected by CVE-2026-19931? +

CVE-2026-19931 affects products from haxx, specifically: curl. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-19931? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-19931