Security Bulletin
Summary
IBM Optim versions 1.0.0, 1.1.0 and 1.2.0 include open-source packages nghttp2 and libarchive that are affected by three high-severity vulnerabilities. IBM Optim 2.0.0 resolves these vulnerabilities by upgrading the affected open-source dependencies to fixed versions.
Vulnerability Details
CVEID: CVE-2026-27135
DESCRIPTION: nghttp2 is an implementation of the Hypertext Transfer Protocol version 2 in C. Prior to version 1.68.1, the nghttp2 library stops reading the incoming data when user facing public API `nghttp2_session_terminate_session` or `nghttp2_session_terminate_session2` is called by the application. They might be called internally by the library when it detects the situation that is subject to connection error. Due to the missing internal state validation, the library keeps reading the rest of the data after one of those APIs is called. Then receiving a malformed frame that causes FRAME_SIZE_ERROR causes assertion failure. nghttp2 v1.68.1 adds missing state validation to avoid assertion failure. No known workarounds are available.
CWE: CWE-617: Reachable Assertion
CVSS Source: security-advisories@github.com
CVSS Base score: 7.5
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
CVEID: CVE-2026-4424
DESCRIPTION: A flaw was found in libarchive. This heap out-of-bounds read vulnerability exists in the RAR archive processing logic due to improper validation of the LZSS sliding window size after transitions between compression methods. A remote attacker can exploit this by providing a specially crafted RAR archive, leading to the disclosure of sensitive heap memory information without requiring authentication or user interaction.
CWE: CWE-125: Out-of-bounds Read
CVSS Source: secalert@redhat.com
CVSS Base score: 7.5
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)
CVEID: CVE-2026-4111
DESCRIPTION: A flaw was identified in the RAR5 archive decompression logic of the libarchive library, specifically within the archive_read_data() processing path. When a specially crafted RAR5 archive is processed, the decompression routine may enter a state where internal logic prevents forward progress. This condition results in an infinite loop that continuously consumes CPU resources. Because the archive passes checksum validation and appears structurally valid, affected applications cannot detect the issue before processing. This can allow attackers to cause persistent denial-of-service conditions in services that automatically process archives.
CWE: CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')
CVSS Source: secalert@redhat.com
CVSS Base score: 7.5
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| IBM Optim | 1.0.0 |
| IBM Optim | 1.1.0 |
| IBM Optim | 1.2.0 |
Remediation/Fixes
Move to IBM Optim 2.0.0
IBM Optim 2.0.0 resolves all three vulnerabilities
libnghttp2 has been upgraded from 1.43.0-6.el9_8.1 to 1.68.1. Version 1.68.1 introduces the missing internal session-state validation that prevents the reachable assertion (CVE-2026-27135).
libarchive has been upgraded from 3.5.3-9.el9_7 to a patched version bundled with Optim 2.0.0. The updated version corrects the LZSS sliding window validation (CVE-2026-4424) and resolves the infinite loop in the RAR5 decompression path (CVE-2026-4111).
Available from https://www.ibm.com/software/passportadvantage/pao-customer
Workarounds and Mitigations
None
Get Notified about Future Security Bulletins
References
Acknowledgement
Change History
21 Sep 2026: Initial Publication
*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.
Disclaimer
According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES ""AS IS"" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.
Document Location
Worldwide
Was this topic helpful?
Document Information
Modified date:
21 September 2026
Initial Publish date:
21 September 2026
UID
ibm17288693