VulnerabilityPublished 28 Jul 2026

CVE-2026-50567: Fission · Zip Slip in pkg/utils/zip.go:Unarchive allows fetcher to write outside the destination directory

Affects github.com/fission/fissionSource GCVE Database

Not known to be exploited · CVSS 7.7 High : upgrade to 1.25.0 soon.

Data as of 27 Oct 2026, 05:11 UTC

CVSS 3.1 base score

7.7High

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.25.0

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: High
Availability: None

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
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 impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Jul 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 github.com/fission/fission to 1.25.0.

Affected software

Product	Affected	Fixed in
Gogithub.com/fission/fission	Affected <1.25.0	Fixed in 1.25.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in github.com/fission/fission version 1.25.0. Users should upgrade to version 1.25.0 or later to ensure that the Unarchive function properly validates archive entry paths and confines extraction to the destination directory. The fix includes rejecting absolute paths, parent directory traversal, and symlink entries, and enforcing filesystem operations within the destination root. Until upgraded, avoid using untrusted zip archives as sources for the fetcher to prevent exploitation.

Description

A Zip Slip vulnerability exists in the Unarchive function of pkg/utils/zip.go in github.com/fission/fission up to version 1.24.0. The function improperly joins archive entry names with the destination directory without validating that the resolved path remains inside the destination. This allows crafted zip entries with directory traversal sequences (e.g., ../../tmp/evil) to write files outside the intended extraction directory. The vulnerability can be triggered when the fetcher downloads and extracts a zip archive, potentially allowing an attacker controlling the archive URL to write files arbitrarily within the file system accessible to the fetcher process.

Impact

An attacker who can supply a crafted zip archive URL to the fetcher sidecar can cause arbitrary files to be written outside the intended extraction directory. This can lead to unauthorized modification or overwriting of files in other tenants' package directories, mounted secret or config volumes, or even the fetcher's own binaries. The vulnerability does not impact confidentiality directly but has a high impact on integrity. Availability impact is not indicated.

Summary

The Unarchive function in pkg/utils/zip.go of github.com/fission/fission versions prior to 1.25.0 concatenates archive entry names with the destination directory using filepath.Join but does not verify that the resulting path is confined within the destination directory. This allows a Zip Slip directory traversal attack where malicious zip entries with relative paths can cause files to be written outside the intended extraction directory. An attacker able to control the Package.Spec.Source.URL or Deployment.URL archive can exploit this to write files anywhere the fetcher process has write access, including other tenants' directories or sensitive mounted volumes. The issue is fixed in version 1.25.0 by validating archive entry names to reject absolute paths, parent directory traversals, and symlinks, and by confining all filesystem operations to the destination root using os.Root.

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #6OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Path Traversal (opens in a new tab)
Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
Using Escaped Slashes in Alternate Encoding (opens in a new tab)
Using Slashes in Alternate Encoding (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

AI analysisMachine-generated, updated 29 Jul 2026, 11:52 UTC

WeaknessesCWE-22

Technical details

References

Community reviews

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