CVE-2026-5438 | Gzip Decompression Bomb via Content-Encoding Header

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.

Published: 2026-04-09 Last update: 2026-04-15 Assigner: [email protected] Source: [email protected]

NVD Status：Analyzed，CVE State: published

View at NVD, CVE.org, EUVD

Threat Intelligence & Risk Assessment for CVE-2026-5438

EPSS CVSS CWE Affected OS Tracker

Conclusion & alert: CVE-2026-5438 is rated Low Risk (35.4/100): CVSS High severity, with low exploitation likelihood (EPSS 0.05%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-5438

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-04-15	0.02%	0.05%	+0.03%
2	2026-04-10	—	0.02%	—

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-5438

CVSS metrics for this CVE.

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.9	3.6	134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-5438

CWE-770 MITRE ↗

OS Trackers for CVE-2026-5438

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2026-5438 not yet assigned priority: Debian including 1 source packages (orthanc), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 3, resolved 2.	https://security-tracker.debian.org/tracker/CVE-2026-5438
`ubuntu`	medium	CVE-2026-5438 medium priority: Ubuntu including 1 source packages (orthanc), 8 status rows across 8 suites (bionic, focal, jammy, noble, questing, resolute, upstream, xenial): needs-triage 8.	https://ubuntu.com/security/CVE-2026-5438

Affected software / configurations for CVE-2026-5438

Vendor	Product	Version	Raw CPE
orthanc-server	orthanc	< 1.12.11	cpe:2.3:a:orthanc-server:orthanc::::::::

References for CVE-2026-5438

URL	Tags
https://kb.cert.org/vuls/id/536588	Third Party Advisory VDB Entry
https://www.machinespirits.de/	Not Applicable
https://www.orthanc-server.com/	Product

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