IO::Uncompress::Unzip: Inefficient Algorithmic Complexity
CVE-2026-48959 is a high-severity inefficient algorithmic complexity vulnerability in IO::Uncompress::Unzip from PMQS, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 2.220 as the first without the flaw, so updating IO::Uncompress::Unzip to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.57% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update IO::Uncompress::Unzip to 2.220 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| PMQS | IO::Uncompress::Unzip | before 2.220 | 2.220 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) | V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.7 and later | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.7 and later | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CISA (ADP).
Official description
IO::Uncompress::Unzip versions before 2.220 for Perl allow CPU exhaustion via per-byte read loop in fastForward. fastForward() compares length $offset (the digit count of the offset, 1 to 19) against the chunk size $c instead of $offset itself, so $c shrinks from 16 KiB to 1-19 bytes per iteration. Extracting a named entry from an attacker supplied zip via IO::Uncompress::Unzip->new($zip, Name => $target) drives a per-byte read loop scaling with the entry's compressed size, up to the non-Zip64 4 GiB cap.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Inefficient Algorithmic Complexity
An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
More Inefficient Algorithmic Complexity vulnerabilities (CWE-407)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
Recent Inefficient Algorithmic Complexity vulnerabilities
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