CVE-2026-18511: IBM i 7.6, 7.5, 7.4, and 7.3 could allow a local authenticated attacker to generate a stack-based buffer overf

Routine

HIGH 7.3REMOTEDOWNGRADE

CVE-2026-18511 is a high-severity flaw (CVSS 7.3) affecting i. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

IBM i 7.6, 7.5, 7.4, and 7.3 could allow a local authenticated attacker to generate a stack-based buffer overflow in the Native IBM i JSSE provider, caused by improper bounds checking during TLS session establishment. A local attacker could overflow a fixed-length buffer and execute arbitrary code on the system or cause the JVM process to crash.

Why this priority

High severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.3 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 78%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-08-13
Last modified	2026-08-17

Publisher (CNA): IBM Corporation · Vendor: ibm

Last updated 2026-08-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-13 21:17 UTCPublished CVE record published
2026-08-17 13:25 UTCUpdated Record last modified

ibm i DOWNGRADE

Affected: 7.3 · 7.4 · 7.5 · 7.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 7.3 (Debian / Ubuntu)

apt-cache madison i sudo apt install i=<VERSION_BEFORE_7.3> sudo apt-mark hold i

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list i sudo dnf downgrade i-<VERSION_BEFORE_7.3> sudo dnf versionlock add i

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-2026-18511?

i: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-18511 being exploited?

CVE-2026-18511 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-2026-18511 affect?

CVE-2026-18511 affects i. Severity is high (CVSS 7.3). IBM i 7.6, 7.5, 7.4, and 7.3 could allow a local authenticated attacker to generate a stack-based buffer overflow in the Native IBM i JSSE provider, caused by improper bounds checking during TLS session establishment. A local attacker could

How urgent is CVE-2026-18511?

Priority 36/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-2311 MEDIUM 6.4 MITIGATE IBM i 7.6, 7.5, 7.4, 7.3, and 7.2 s vulnerable to privilege escalation caused by an invalid IBM i Web Administ
CVE-2026-7870 HIGH 8.8 MITIGATE IBM i 7.6, 7.5, 7.4, and 7.3 could allow a user to gain elevated privileges due to an unqualified library call
CVE-2026-9072 HIGH 8.1 UPGRADE IBM WebSphere Application Server and IBM WebSphere Application Server Liberty - when using Intelligent Managem
CVE-2026-10852 MEDIUM 5.9 MITIGATE IBM WebSphere Application Server and IBM WebSphere Application Server Liberty are vulnerable to denial of serv
CVE-2026-8858 HIGH 7.5 UPGRADE IBM WebSphere Application Server and IBM WebSphere Application Server Liberty are vulnerable to remote code ex

References

← Back to latest CVEs