CVE-2026-39998: Improper Input Validation vulnerability in Apache APISIX. The attacker can take advantage of certain configur

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HIGH 8.8WATCHLISTUPGRADE

CVE-2026-39998 is a high-severity flaw (CVSS 8.8) affecting apisix. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Input Validation vulnerability in Apache APISIX. The attacker can take advantage of certain configuration in forward-auth plugin to spoof identity headers. This issue affects Apache APISIX: from 2.12.0 through 3.16.0. Users are recommended to upgrade to version 3.17.0, which fixes the issue.

Why this priority

High severity
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.7% (top 48%)
CISA exploited list	No
Weakness	CWE-20
Published	2026-06-19
Last modified	2026-10-26

Publisher (CNA): Apache Software Foundation · Vendor: apache

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-19 14:16 UTCPublished CVE record published
2026-10-26 11:10 UTCUpdated Record last modified

apache apisix UPGRADE

Affected: >= 2.12.0 and < 3.17.0

Fixed in: 3.17.0

Safe to downgrade to: a release before 2.12.0

1. Check installed version

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

2. UPGRADE to 3.17.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade apisix

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 2.12.0 (Debian / Ubuntu)

apt-cache madison apisix sudo apt install apisix=<VERSION_BEFORE_2.12.0> sudo apt-mark hold apisix

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

dnf --showduplicates list apisix sudo dnf downgrade apisix-<VERSION_BEFORE_2.12.0> sudo dnf versionlock add apisix

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.

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-2026-39998?

apisix: upgrade to 3.17.0. Exact commands for each OS are on this page.

Is CVE-2026-39998 being exploited?

CVE-2026-39998 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-2026-39998 affect?

CVE-2026-39998 affects apisix. Severity is high (CVSS 8.8). Improper Input Validation vulnerability in Apache APISIX. The attacker can take advantage of certain configuration in forward-auth plugin to spoof identity headers. This issue affects Apache APISIX: from 2.12.0 through 3.16.0. Users are r

How urgent is CVE-2026-39998?

Priority 49/100. High severity; On your watchlist

Software pages

Apache APISIX vulnerabilities

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References

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