CVE-2026-78594: Improper Handling of Highly Compressed Data (CWE-409) in APM Server can lead to a persistent denial of service

Routine

MEDIUM 4.9UPGRADE

CVE-2026-78594 is a medium-severity flaw (CVSS 4.9) affecting apm server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Handling of Highly Compressed Data (CWE-409) in APM Server can lead to a persistent denial of service via Excessive Allocation (CAPEC-130). An authenticated user with write access to source map content could store specially crafted, highly compressed content that exhausts the memory available to APM Server when it is later processed, terminating the process. The condition recurs on every restart until the stored content is removed.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.9 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	None
EPSS exploit chance	0.5% (top 57%)
CISA exploited list	No
Weakness	CWE-409
Published	2026-09-02
Last modified	2026-09-03

Publisher (CNA): Elastic · Vendor: elastic

Last updated 2026-09-03 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-02 15:17 UTCPublished CVE record published
2026-09-03 19:13 UTCUpdated Record last modified

elastic apm server UPGRADE

Affected: >= 8.0.0 and < 8.19.20 · >= 9.0.0 and < 9.4.5 · 9.5.0

Fixed in: 8.19.20, 9.4.5

Safe to downgrade to: a release before 8.0.0

1. Check installed version

apt-cache policy apm-server || rpm -q apm-server || apm-server --version

2. UPGRADE to 8.19.20 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade apm-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade apm-server

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 8.0.0 (Debian / Ubuntu)

apt-cache madison apm-server sudo apt install apm-server=<VERSION_BEFORE_8.0.0> sudo apt-mark hold apm-server

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

dnf --showduplicates list apm-server sudo dnf downgrade apm-server-<VERSION_BEFORE_8.0.0> sudo dnf versionlock add apm-server

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-2026-78594?

apm server: upgrade to 8.19.20, 9.4.5. Exact commands for each OS are on this page.

Is CVE-2026-78594 being exploited?

CVE-2026-78594 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-2026-78594 affect?

CVE-2026-78594 affects apm server. Severity is medium (CVSS 4.9). Improper Handling of Highly Compressed Data (CWE-409) in APM Server can lead to a persistent denial of service via Excessive Allocation (CAPEC-130). An authenticated user with write access to source map content could store specially crafted

How urgent is CVE-2026-78594?

Priority 28/100. No elevated risk signals yet.

References

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