CVE-2026-19931: A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authent

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CRITICAL 9.8REMOTEUPGRADE

CVE-2026-19931 is a critical-severity flaw (CVSS 9.8) affecting curl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Critical severity
Public exploit reference
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.1% (top 34%)
CISA exploited list	No
Weakness	CWE-488
Published	2026-09-06
Last modified	2026-09-15

Publisher (CNA): curl · Vendor: haxx

Last updated 2026-09-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-06 18:17 UTCPublished CVE record published
2026-09-15 07:16 UTCUpdated Record last modified

haxx curl UPGRADE

Affected: >= 7.64.1 and < 8.22.0

Fixed in: 8.22.0

Safe to downgrade to: a release before 7.64.1

1. Check installed version

apt-cache policy curl || rpm -q curl || curl --version

2. UPGRADE to 8.22.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade curl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade curl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 7.64.1 (Debian / Ubuntu)

apt-cache madison curl sudo apt install curl=<VERSION_BEFORE_7.64.1> sudo apt-mark hold curl

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list curl sudo dnf downgrade curl-<VERSION_BEFORE_7.64.1> sudo dnf versionlock add curl

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Fedora 46 · ddnet · FIXED · 20.2-1.fc46 · FEDORA-2026-6991b4ab14 · source

sudo dnf upgrade --advisory=FEDORA-2026-6991b4ab14

Fedora ELN · libplacebo · FIXED · 7.360.1-5.eln159 · FEDORA-2026-92226f221e · source

sudo dnf upgrade --advisory=FEDORA-2026-92226f221e

Debian 12 · curl · NO FIX YET

Debian 13 · curl · NO FIX YET

RHEL 10 · curl · NO FIX YET

RHEL 10 · igvm · NO FIX YET

RHEL 10 · rust · NOT AFFECTED

RHEL 10 · s390utils · NOT AFFECTED

RHEL 10 · snphost · NO FIX YET

Alpine 3.23 · curl · FIXED · curl-8.22.0-r0

apk add --upgrade curl apk info -v curl

Alpine 3.24 · curl · FIXED · curl-8.22.0-r0

apk add --upgrade curl apk info -v curl

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-19931?

curl: upgrade to 8.22.0. Exact commands for each OS are on this page.

Is CVE-2026-19931 being exploited?

CVE-2026-19931 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-19931 affect?

CVE-2026-19931 affects curl. Severity is critical (CVSS 9.8). 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 previousl

How urgent is CVE-2026-19931?

Priority 64/100. Critical severity; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

curl vulnerabilities

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References

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