Sink boundary: A format string controls how another value is interpreted during output or logging.
The pack does not provide a callable signature for this record; the watched access path is shown directly.
| Arg | Access path | Purpose | Watched |
|---|---|---|---|
| Argument[1] | Argument[1] | The access path Atropos marks for this model. | ▲ sink |
CWE-134 ↗
Externally-Controlled Format String
A format string originates from an external source and controls formatting behavior.
Attacker's-eye view · format-string
An attacker supplies format directives that read memory, write memory, or alter output behavior.
// modeled boundary: Argument[1]
vfprintf(attacker_influenced_value);
1Keep the format string constant.
2Pass external data as a value argument.
3Check size and encoding limits.
These checks require the surrounding codebase. The model names the boundary; it does not decide reachability or prove that a guard dominates every path.
Is this a bug in your code?Atropos stops here — by design
Atropos identifies Argument[1] as a format-string sink. It cannot see whether untrusted data reaches this call in your repository.
Lachesis is the codebase-level step: it traces reachability and guards for this symbol.
Check this symbol in Lachesis →Across languages
No cross-language match.
What neutralizes it
No sanitizer of this kind is modeled.
Model facts · verbatim from the pack
| Role | Kind | Access path | Model ID | Confidence |
|---|---|---|---|---|
| sink | format-string | Argument[1] | c.std.vfprintf.a1 | high · corrob. 3 |