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Vulnerabilities

Vulnerability · USN-8954-1

zlib vulnerability

Published Oct 22, 2026 · catalog updated Oct 23, 2026 · the affected product

Open the advisory

Exploitation likelihood is not on this record for USN-8954-1. A missing EPSS score is not a low risk. Compare the affected product with the linked advisory before you change production.

Gaps on this record

  • No plain product name is stored. The page cannot tell you which product to check.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
  • EPSS is missing. A missing score is not a low risk.
Severity
Unknown—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
Awaiting synchronization with FIRST
Remediation
Advisory link
Affected products
Ubuntu:24.04:LTS zlib · Ubuntu:26.04:LTS zlib · Ubuntu:26.10 zlib

Ali Firas discovered that zlib incorrectly handled certain non-blocking write operations. An attacker could possibly use this issue to trigger a heap buffer overflow, resulting in a denial of service or arbitrary code execution.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Ubuntu:24.04:LTS zlib0 → 1:1.3.dfsg-3.1ubuntu2.3
  • Ubuntu:26.04:LTS zlib0 → 1:1.3.dfsg+really1.3.1-1ubuntu3.2
  • Ubuntu:26.10 zlib0 → 1:1.3.dfsg+really1.3.2-3ubuntu1.1

How to fix USN-8954-1

  • Recommended remediation

    A patch or advisory reference is linked. Open the original publisher for availability by product version.

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

Exploitation likelihood is not on this record for USN-8954-1. A missing EPSS score is not a low risk. Compare the affected product with the linked advisory before you change production.

Which versions are affected?

Compare what you have installed with 0 → 1:1.3.dfsg-3.1ubuntu2.3, 0 → 1:1.3.dfsg+really1.3.1-1ubuntu3.2, 0 → 1:1.3.dfsg+really1.3.2-3ubuntu1.1. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS is not on this record yet. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Ubuntu security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 22, 2026 · OpenSSF OSV / OSV Scanner

    Detected

    Ali Firas discovered that zlib incorrectly handled certain non-blocking write operations. An attacker could possibly use this issue to trigger a heap buffer overflow, resulting in a denial of service or arbitrary code execution.

  2. Oct 23, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    zlib fixed in 1:1.3.dfsg-3.1ubuntu2.3; zlib fixed in 1:1.3.dfsg+really1.3.2-3ubuntu1.1; zlib fixed in 1:1.3.dfsg+really1.3.1-1ubuntu3.2

  3. Oct 23, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    zlib fixed in 1:1.3.dfsg-3.1ubuntu2.3

  4. Oct 23, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    zlib fixed in 1:1.3.dfsg+really1.3.2-3ubuntu1.1

  5. Oct 23, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    zlib fixed in 1:1.3.dfsg+really1.3.1-1ubuntu3.2

  6. Oct 23, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    Ali Firas discovered that zlib incorrectly handled certain non-blocking write operations. An attacker could possibly use this issue to trigger a heap buffer overflow, resulting in a denial of service or arbitrary code execution.

Sources

References

Freshness

Last verified in this catalog Oct 23, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.