CVE-2026-18212: Keycloak-services: keycloak-services: saml redirect deflate helpers leak native zlib state
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 0.7%
Up from 0.5% on .
EPSS score, percentile 53.2 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 7.5 High
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
- Which versions are affected?
Unaffected 26.4.16-2; 26.4-26; 26.4-26; 26.6.7-3; 26.6-20; 26.6-20
Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Workaround (from the CVE record)
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Advisories and patches
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Unaffected | 26.4.16-2 |
Versions not listed are: affected.
| Status | Versions |
|---|---|
| Unaffected | 26.4-26 |
Versions not listed are: affected.
| Status | Versions |
|---|---|
| Unaffected | 26.4-26 |
Versions not listed are: affected.
| Status | Versions |
|---|
Versions not listed are: unaffected.
| Status | Versions |
|---|
Versions not listed are: unaffected.
| Status | Versions |
|---|---|
| Unaffected | 26.6.7-3 |
Versions not listed are: affected.
| Status | Versions |
|---|---|
| Unaffected | 26.6-20 |
Versions not listed are: affected.
| Status | Versions |
|---|---|
| Unaffected | 26.6-20 |
Versions not listed are: affected.
| Status | Versions |
|---|
Versions not listed are: unaffected.
| Status | Versions |
|---|
Versions not listed are: unaffected.
| Status | Versions |
|---|
Versions not listed are: unaffected.
| Status | Versions |
|---|
Versions not listed are: affected.
| Status | Versions |
|---|
Versions not listed are: unaffected.
| Status | Versions |
|---|
Versions not listed are: affected.
Versions the record lists as unaffected: 26.4.16-2, 26.4-26, 26.6.7-3, 26.6-20.
Source: CVE List, as of . About the data.
About this vulnerability
A flaw was found in the SAML Redirect Binding implementation of Keycloak, an open-source identity and access management solution. The issue occurs because the custom DEFLATE compression and decompression helpers fail to release native zlib memory after use. An unauthenticated attacker can exploit this by sending repeated malformed SAML requests, leading to native memory exhaustion and a denial of…
Summary: CVE record, as of .
- CISA has not added CVE-2026-18212 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
- The CVE record was published on 16 Sep 2026.
- The CVE record carries a CVSS v3.1 base score of 7.5 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.7% (percentile 53.2), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable yes, technical impact partial.
- The credits in the CVE record name OpenAI as finder.
Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
Keycloak-services: keycloak-services: saml redirect deflate helpers leak native zlib state
A flaw was found in the SAML Redirect Binding implementation of Keycloak, an open-source identity and access management solution. The issue occurs because the custom DEFLATE compression and decompression helpers fail to release native zlib memory after use. An unauthenticated attacker can exploit this by sending repeated malformed SAML requests, leading to native memory exhaustion and a denial of service.
Source: CVE List, as of . About the data.
Weakness
CWE-401
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published |
References
2
Known exploited Red Hat vulnerabilities
- CVE-2015-3246: Red Hat Libuser Race Condition Vulnerability
- CVE-2015-5287: Red Hat Automatic Bug Reporting Tool Privilege Escalation Vulnerability
- CVE-2018-14667: Red Hat JBoss RichFaces Framework Expression Language Injection Vulnerability
- CVE-2021-3560: Red Hat Polkit Incorrect Authorization Vulnerability
- CVE-2021-4034: Red Hat Polkit Out-of-Bounds Read and Write Vulnerability