CVE-2026-72639: Elasticsearch does not enforce an upper bound on a user-supplied count accepted by a search highlighting optio

Routine

MEDIUM 6.5UPGRADE

CVE-2026-72639 is a medium-severity flaw (CVSS 6.5) affecting elasticsearch. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Elasticsearch does not enforce an upper bound on a user-supplied count accepted by a search highlighting option, and the allocation derived from that count is not accounted against any circuit breaker. An authenticated user holding only read privileges on a single searchable index can submit one small search request that causes the node to reserve an excessively large internal data structure. The allocation occurs before the existing highlighting

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Weakness	CWE-789
Published	2026-08-13
Last modified	2026-09-01

Publisher (CNA): Elastic · Vendor: elastic

Last updated 2026-09-01 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-13 20:17 UTCPublished CVE record published
2026-09-01 14:08 UTCUpdated Record last modified

elastic elasticsearch UPGRADE

Affected: >= 8.19.0 and < 8.19.20 · >= 9.3.0 and < 9.4.5 · >= 9.5.0 and < 9.5.1

Fixed in: 8.19.20, 9.4.5, 9.5.1

Safe to downgrade to: a release before 8.19.0

1. Check installed version

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

2. UPGRADE to 8.19.20 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade elasticsearch

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 8.19.0 (Debian / Ubuntu)

apt-cache madison elasticsearch sudo apt install elasticsearch=<VERSION_BEFORE_8.19.0> sudo apt-mark hold elasticsearch

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

dnf --showduplicates list elasticsearch sudo dnf downgrade elasticsearch-<VERSION_BEFORE_8.19.0> sudo dnf versionlock add elasticsearch

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-2026-72639?

elasticsearch: upgrade to 8.19.20, 9.4.5, 9.5.1. Exact commands for each OS are on this page.

Is CVE-2026-72639 being exploited?

CVE-2026-72639 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-2026-72639 affect?

CVE-2026-72639 affects elasticsearch. Severity is medium (CVSS 6.5). Elasticsearch does not enforce an upper bound on a user-supplied count accepted by a search highlighting option, and the allocation derived from that count is not accounted against any circuit breaker. An authenticated user holding only rea

How urgent is CVE-2026-72639?

Priority 32/100. No elevated risk signals yet.

Software pages

Elasticsearch vulnerabilities

Related CVEs

CVE-2026-56148 MEDIUM 6.5 UPGRADE Uncontrolled Recursion (CWE-674) in Elasticsearch can lead to a denial of service via Excessive Allocation (CA
CVE-2026-49090 MEDIUM 6.5 UPGRADE Uncontrolled Resource Consumption (CWE-400) in Elasticsearch can lead to a denial of service via Excessive All
CVE-2026-56149 MEDIUM 4.9 UPGRADE Allocation of Resources Without Limits or Throttling (CWE-770) in Elasticsearch can lead to a denial of servic
CVE-2026-56145 MEDIUM 6.5 UPGRADE Uncontrolled Resource Consumption (CWE-400) in Elasticsearch can lead to denial of service via Excessive Alloc
CVE-2026-63136 MEDIUM 6.5 UPGRADE Uncontrolled Resource Consumption (CWE-400) in Elasticsearch can lead to denial of service via Excessive Alloc

References

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