CVE-2026-5438: A gzip decompression bomb vulnerability exists when Orthanc processes HTTP request with `Content-Encoding: gzi

Q: How do I fix CVE-2026-5438?

orthanc: upgrade to 1.12.11. Exact commands for each OS are on this page.

Q: Is CVE-2026-5438 being exploited?

CVE-2026-5438 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-5438 affect?

CVE-2026-5438 affects orthanc. Severity is high (CVSS 7.5). A gzip decompression bomb vulnerability exists when Orthanc processes HTTP request with `Content-Encoding: gzip`. The server does not enforce limits on decompressed size and allocates memory based on attacker-controlled compression metadata

Q: How urgent is CVE-2026-5438?

Priority 42/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADE

CVE-2026-5438 is a high-severity flaw (CVSS 7.5) affecting orthanc. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A gzip decompression bomb vulnerability exists when Orthanc processes HTTP request with `Content-Encoding: gzip`. The server does not enforce limits on decompressed size and allocates memory based on attacker-controlled compression metadata. A specially crafted gzip payload can trigger excessive memory allocation and exhaust system memory.

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 59%)
CISA exploited list	No
Weakness	CWE-770
Published	2026-04-09
Last modified	2026-10-26

Publisher (CNA): CERT/CC · Vendor: orthanc-server

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

Am I affected?

Timeline

2026-04-09 15:16 UTCPublished CVE record published
2026-10-26 00:10 UTCUpdated Record last modified

orthanc-server orthanc UPGRADE

Affected: < 1.12.11

Fixed in: 1.12.11

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.12.11 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade orthanc

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

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-2026-5438?

orthanc: upgrade to 1.12.11. Exact commands for each OS are on this page.

Is CVE-2026-5438 being exploited?

CVE-2026-5438 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-2026-5438 affect?

CVE-2026-5438 affects orthanc. Severity is high (CVSS 7.5). A gzip decompression bomb vulnerability exists when Orthanc processes HTTP request with `Content-Encoding: gzip`. The server does not enforce limits on decompressed size and allocates memory based on attacker-controlled compression metadata

How urgent is CVE-2026-5438?

Priority 42/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-5444 HIGH 7.1 UPGRADE A heap buffer overflow vulnerability exists in the PAM image parsing logic

References

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