CVE-2026-6540: Calico's Application Layer Policy (disabled by default), which enforces HTTP rules through Dikastes, fails to

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HIGH 7.5REMOTEUPGRADE

CVE-2026-6540 is a high-severity flaw (CVSS 7.5) affecting calico. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Calico's Application Layer Policy (disabled by default), which enforces HTTP rules through Dikastes, fails to perform URL path normalization. As a result, HTTP requests using path-traversal segments, encoded slashes, or repeated slashes are not correctly evaluated by Prefix path rules. Dikastes authorizes the request under the permitted prefix while the downstream workload or a fronting proxy normalizes the path and serves the restricted endpoint

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 55%)
CISA exploited list	No
Weakness	CWE-22, CWE-23
Published	2026-07-30
Last modified	2026-08-08

Publisher (CNA): Tigera, Inc. · Vendor: tigera

Last updated 2026-08-08 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-30 15:16 UTCPublished CVE record published
2026-08-08 01:10 UTCUpdated Record last modified

tigera calico UPGRADE

Affected: < 3.21.7 · < 3.31.6 · <= 22.4.0 · >= 3.22.0 and < 3.22.4 · >= 3.32.0 and < 3.32.1

Fixed in: 3.21.7, 3.22.4, 3.31.6, 3.32.1

Safe to downgrade to: a release before 3.22.0

1. Check installed version

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

2. UPGRADE to 3.21.7 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade calico

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 3.22.0 (Debian / Ubuntu)

apt-cache madison calico sudo apt install calico=<VERSION_BEFORE_3.22.0> sudo apt-mark hold calico

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

dnf --showduplicates list calico sudo dnf downgrade calico-<VERSION_BEFORE_3.22.0> sudo dnf versionlock add calico

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-2026-6540?

calico: upgrade to 3.21.7, 3.22.4, 3.31.6, 3.32.1. Exact commands for each OS are on this page.

Is CVE-2026-6540 being exploited?

CVE-2026-6540 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-2026-6540 affect?

CVE-2026-6540 affects calico. Severity is high (CVSS 7.5). Calico's Application Layer Policy (disabled by default), which enforces HTTP rules through Dikastes, fails to perform URL path normalization. As a result, HTTP requests using path-traversal segments, encoded slashes, or repeated slashes are

How urgent is CVE-2026-6540?

Priority 43/100. High severity; Remotely exploitable, no login, no user action

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References

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