wasmtime: UNIX Symbolic Link (Symlink) Following
CVE-2026-118688 is a high-severity UNIX symbolic link (symlink) following vulnerability in wasmtime from Bytecodealliance, with a CVSS 3.1 base score of 7.9 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, but only if a user takes part, for example by opening a link or file. The record lists versions 36.0.18, 48.0.6, 49.0.3 as the first without the flaw, so updating wasmtime to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.24% 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 wasmtime to 36.0.18 or 48.0.6 or 49.0.3, whichever matches your release line, or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Bytecodealliance | wasmtime | before 36.0.18; 37.0.0 up to, but not including, 48.0.6; 49.0.0 up to, but not including, 49.0.3 | 36.0.18, 48.0.6, 49.0.3 |
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
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- LowA basic user account is enough.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:L. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.8 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 7.9 | High | CNA (vulncheck.com) |
Official description
wasmtime-wasi in Wasmtime before 36.0.18, 37.0.0 before 48.0.6, and 49.0.0 before 49.0.3 re-appends a trailing slash to rename source paths, causing renameat on macOS and FreeBSD hosts to follow directory symlinks. A guest with sandbox write access can rename a relative symlink such as "up/" to move host directories into its sandbox and read or write them.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: UNIX Symbolic Link (Symlink) Following
The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.
How developers prevent this class of flaw
- Symbolic link attacks often occur when a program creates a tmp directory that stores files/links. Access to the directory should be restricted to the program as to prevent attackers from manipulating the files.
- Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
More UNIX Symbolic Link (Symlink) Following vulnerabilities (CWE-61)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in wasmtime
- 9.9 Critical severity
- 9.9 Critical severity
- 7.9 High severity
- 9.9 Critical severity
Recent UNIX Symbolic Link (Symlink) Following vulnerabilities
- 9.4 Critical severity
- 7.1 High severity
- 7.1 High severity
- 7.4 High severity
- 9.8 Critical severity
- 7.4 High severity
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