CVE-2026-78605: Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') (CWE-444) in Elasticsearch can lead to

Routine

MEDIUM 5.9REMOTEUPGRADE

CVE-2026-78605 is a medium-severity flaw (CVSS 5.9) affecting elasticsearch. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') (CWE-444) in Elasticsearch can lead to information disclosure via HTTP Request Smuggling (CAPEC-33). Under specific proxy deployment configurations, a network attacker could obtain confidential responses intended for other authenticated users.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 73%)
CISA exploited list	No
Weakness	CWE-444
Published	2026-09-01
Last modified	2026-09-02

Publisher (CNA): Elastic · Vendor: elastic

Last updated 2026-09-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-01 20:17 UTCPublished CVE record published
2026-09-02 18:50 UTCUpdated Record last modified

elastic elasticsearch UPGRADE

Affected: >= 8.18.0 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 8.18.0

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 8.18.0 (Debian / Ubuntu)

apt-cache madison elasticsearch sudo apt install elasticsearch=<VERSION_BEFORE_8.18.0> 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_8.18.0> 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-2026-78605?

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

Is CVE-2026-78605 being exploited?

CVE-2026-78605 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-2026-78605 affect?

CVE-2026-78605 affects elasticsearch. Severity is medium (CVSS 5.9). Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') (CWE-444) in Elasticsearch can lead to information disclosure via HTTP Request Smuggling (CAPEC-33). Under specific proxy deployment configurations, a network attacker

How urgent is CVE-2026-78605?

Priority 32/100. Remotely exploitable, no login, no user action

Software pages

Elasticsearch vulnerabilities

Related CVEs

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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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