How severe is CVE-2026-59901?

CVE-2026-59901 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-59901 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-59901?

CVE-2026-59901 affects Netty. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-59901?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-59901 published?

CVE-2026-59901 was published on 2026-07-29 and last updated on 2026-08-06.

CVE-2026-59901

CVE-2026-59901 is a high-severity vulnerability in Netty with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-835.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 8.7
EPSS exploit prediction: 0% (18th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-835
Affected product: Netty
Published: 2026-07-29
Last modified: 2026-08-06

Description

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, the `Bzip2Decoder` handler in Netty's compression codec pipeline is vulnerable to a denial-of-service attack through a malformed bzip2 stream that permanently captures the event-loop thread in an infinite loop. The vulnerability exists in the run-length encoding (RLE) state machine within [`Bzip2BlockDecompressor.read()`]. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

Frequently asked questions

What is CVE-2026-59901?: Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, the `Bzip2Decoder` handler in Netty's compression codec pipeline is vulnerable to a denial-of-service attack through a malformed bzip2 stream that permanently captures the event-loop thread in an infinite loop. The vulnerability exists in the run-length encoding (RLE) state machine within [`Bzip2BlockDecompressor.read()`]. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.
How severe is CVE-2026-59901?: CVE-2026-59901 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-59901 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-59901?: CVE-2026-59901 affects Netty. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-59901?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-59901 published?: CVE-2026-59901 was published on 2026-07-29 and last updated on 2026-08-06.

References

https://github.com/netty/netty/security/advisories/GHSA-558v-64gr-wgg4

Affected products (1)

cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*

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