CVE-2026-9079: libcurl had a flaw that when instructed to clear proxy authentication credentials which made it not do so, lea

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CRITICAL 9.8REMOTEUPGRADE

CVE-2026-9079 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.

libcurl had a flaw that when instructed to clear proxy authentication credentials which made it not do so, leaving the old credentials around to get used for subsequent transfers that should not know nor use them.

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 36%)
CISA exploited list	No
Weakness	CWE-522
Published	2026-07-03
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

2026-07-03 07:16 UTCPublished CVE record published
2026-09-15 07:16 UTCUpdated Record last modified

haxx curl UPGRADE

Affected: >= 8.8.0 and < 8.21.0

Fixed in: 8.21.0

Safe to downgrade to: a release before 8.8.0

1. Check installed version

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

2. UPGRADE to 8.21.0 (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 8.8.0 (Debian / Ubuntu)

apt-cache madison curl sudo apt install curl=<VERSION_BEFORE_8.8.0> 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_8.8.0> 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 · rubygem-mechanize · FIXED · 2.14.2-1.fc46 · FEDORA-2026-d2e3b5fc5d · source

sudo dnf upgrade --advisory=FEDORA-2026-d2e3b5fc5d

Fedora ELN · opkssh · FIXED · 0.19.1-1.eln159 · FEDORA-2026-45a9706969 · source

sudo dnf upgrade --advisory=FEDORA-2026-45a9706969

Ubuntu 20.04 · curl · NOT AFFECTED

Ubuntu 22.04 · curl · NOT AFFECTED

Ubuntu 24.04 · curl · NOT AFFECTED

Ubuntu 25.10 · curl · FIXED · 8.14.1-2ubuntu1.4

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "8.14.1-2ubuntu1.4" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · curl · NOT AFFECTED

Debian 13 · curl · NO FIX YET

RHEL 10 · curl · FIXED · curl-8.12.1-4.el10_2.6

sudo dnf upgrade --advisory=RHSA-2026:69125 rpm -q curl

RHEL 10.0 Extended Update Support · curl · FIXED · curl-8.12.1-1.el10_0.10

sudo dnf upgrade --advisory=RHSA-2026:72506 rpm -q curl

RHEL 10 · igvm · NOT AFFECTED

RHEL 10 · rust · NOT AFFECTED

RHEL 10 · s390utils · NOT AFFECTED

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

apk add --upgrade curl apk info -v curl

Alpine 3.24 · curl · FIXED · curl-8.21.0-r0

apk add --upgrade curl apk info -v curl

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-2132 · source

sudo dnf update --advisory=ALAS2023-2026-2132

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-2026-9079?

curl: upgrade to 8.21.0. Exact commands for each OS are on this page.

Is CVE-2026-9079 being exploited?

CVE-2026-9079 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-2026-9079 affect?

CVE-2026-9079 affects curl. Severity is critical (CVSS 9.8). libcurl had a flaw that when instructed to clear proxy authentication credentials which made it not do so, leaving the old credentials around to get used for subsequent transfers that should not know nor use them.

How urgent is CVE-2026-9079?

Priority 63/100. 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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