CVE-2026-102474
Description
A flaw was found in dash. The printf builtin reserves four bytes before converting a Unicode \u or \U escape, but the multi-byte token can need five or six bytes. A local user who can supply such an escape to dash printf or echo %b, including through dash -c and a positional argument, can write one or two bytes past that reservation.
Statement
This vulnerability is rated as Moderate severity because exploitation requires local access and the ability to pass crafted Unicode escape sequences directly into the shell's built-in formatting utilities. In Red Hat Enterprise Linux, dash is not deployed as the default system shell (/bin/sh is linked to bash), restricting exposure primarily to environments where dash is deliberately installed and executed on untrusted input. Consequently, the flaw presents a limited blast radius consisting of out-of-bounds heap memory corruption without direct privilege escalation under standard operating conditions.
Mitigation
No practical runtime mitigation is available in the shipped build. Do not pass untrusted data into dash printf/echo %b or into dash -c as a positional argument. The fix is to raise the CHECKSTRSPACE reservation at both printf call sites to 8. The later unaligned-access memcpy change in conv_escape does not enlarge that reservation and does not fix this issue.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4 | N/A | 4 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
Acknowledgements
Red Hat would like to thank Shubham Raj (Causal Security) for reporting this issue.
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