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Response snapshot Oct 31, 2026, 01:26 UTC

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VulnerabilityCVE-2026-119276

MariaDB Connector/J: Rogue server can drive large heap allocations from server-declared lengths in OK packets

MariaDB Connector/J sized heap allocations from lengths declared by the server in OK packets before checking that those lengths fit in the packet. A rogue or MitM server can make the client allocate megabytes from a packet of a few bytes.

At a glance

Exploited
Not known
Severity
5.9 Medium (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: org.mariadb.jdbc:mariadb-java-client: 3.3.7; org.mariadb.jdbc:mariadb-java-client: 3.4.5; org.mariadb.jdbc:mariadb-java-client: 3.5.11. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-h599-m3w5-9m7x (opens a new tab)

What happened

Summary

MariaDB Connector/J sized heap allocations from lengths declared by the server in OK packets before checking that those lengths fit in the packet. A rogue or MitM server can make the client allocate megabytes from a packet of a few bytes.

Details

When CLIENT_SESSION_TRACK is negotiated (the default), an OK packet carries an info field followed by session-state blocks, each tracked variable being sent as a length-encoded name and value. OkPacket.parse() and parseWithInfo() allocated new byte[len] for the info field, the variable name and the value with the server-declared len, then copied the packet data into it.

Continue reading

The copy failed with an ArrayIndexOutOfBoundsException when the packet was shorter, but only after the allocation had taken place.

A server-declared length of 8 MiB in an 18-byte packet was enough to trigger an 8 MiB allocation; the integer-range validation of length-encoded values does not help, since such lengths are valid positive integers.

The fix validates every server-declared length against the remaining packet bytes before any allocation (ReadableByteBuf.checkLength() and a bounded readBytes(int)), and stops reading the session state at the first inconsistent entry.

Impact

Availability only: a malicious or compromised server, or a MitM, can drive attacker-controlled heap allocations on every OK packet, creating GC pressure up to OutOfMemoryError in the client application. Exploitation requires control of the server side of the connection; no authentication bypass, confidentiality or integrity impact.

Credit

Reported by fg0x0

Affected package ranges reported by GitHub: org.mariadb.jdbc:mariadb-java-client: >= 3.0.0, < 3.3.7 org.mariadb.jdbc:mariadb-java-client: >= 3.4.0, < 3.4.5 org.mariadb.jdbc:mariadb-java-client: >= 3.5.0, < 3.5.11

Scores and how they were measured

CVSS base severity

5.9

Version 3.1As of

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-h599-m3w5-9m7x (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h599-m3w5-9m7x, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 30). MariaDB Connector/J: Rogue server can drive large heap allocations from server-declared lengths in OK packets (CVE-2026-119276). https://kevwire.com/record/CVE-2026-119276

MLA

"MariaDB Connector/J: Rogue server can drive large heap allocations from server-declared lengths in OK packets (CVE-2026-119276)." KEVWire, 30 Oct. 2026, kevwire.com/record/CVE-2026-119276.

Chicago

KEVWire. "MariaDB Connector/J: Rogue server can drive large heap allocations from server-declared lengths in OK packets (CVE-2026-119276)." Last modified October 30, 2026. https://kevwire.com/record/CVE-2026-119276.

Evidence summary (plain text)

MariaDB Connector/J: Rogue server can drive large heap allocations from server-declared lengths in OK packets (Oct 30, 2026).
MariaDB Connector/J sized heap allocations from lengths declared by the server
in OK packets before checking that those lengths fit in the packet. A rogue or
MitM server can make the client allocate megabytes from a packet of a few bytes.

When CLIENT_SESSION_TRACK is negotiated (the default), an OK packet carries an
info field followed by session-state blocks, each tracked variable being sent as a
length-encoded name and value.
CVSS 5.9 (version 3.1; evidence as of Oct 30, 2026; https://github.com/advisories/GHSA-h599-m3w5-9m7x).
Sources:
GitHub-reviewed advisory GHSA-h599-m3w5-9m7x: https://github.com/advisories/GHSA-h599-m3w5-9m7x
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-119276.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 31, 2026, 00:50 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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