CyberSecBulletin
CVE-2026-19931NVD status: Modified

curl: Exposure of Data Element to Wrong Session

Published Updated By the CyberSecBulletin desk

CVE-2026-19931 is a critical-severity exposure of data element to wrong session vulnerability in curl, with a CVSS 3.1 base score of 9.8 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 0.75% chance of exploitation within 30 days, higher than 55% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. 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.
  2. Read the advisory on curl.se for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Curlcurl7.64.1 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; 6c6035532383e300c712e4c1cd9fdd749ed5cf59 up to, but not including, 7103a93b05bc69ea98ed9d05d02fa9eeba533f2f; 8.21.0; 8.20.0; 8.19.0; and 32 more ranges8.14.2, 8.16.1, 8.20.1, 8.22.0, 7103a93b05bc69ea98ed9d05d02fa9eeba533f2f

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
LowNo special conditions are needed; the attack works reliably.
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
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CISA (ADP).

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Exposure of Data Element to Wrong Session

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.

How developers prevent this class of flaw

  • Protect the application's sessions from information leakage. Make sure that a session's data is not used or visible by other sessions.
  • Use a static analysis tool to scan the code for information leakage vulnerabilities (e.g. Singleton Member Field).
  • In a multithreading environment, storing user data in Servlet member fields introduces a data access race condition. Do not use member fields to store information in the Servlet.

More Exposure of Data Element to Wrong Session vulnerabilities (CWE-488)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Patches and release notes

Other vulnerabilities in curl

All curl vulnerabilities

Recent Exposure of Data Element to Wrong Session vulnerabilities

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