Medium [CVE-2026-49839] Heap out-of-bounds write via oversized raw file processing

jq is a command-line JSON processor. Prior to 1.8.2,` jq --rawfile` can turn a handled oversized-string error into invalid-state reuse and a real heap out-of-bounds write in assertion-disabled builds.

When jv_load_file(raw=1) reads an attacker-controlled file, it repeatedly appends file chunks to the same jv string accumulator. Once jv_string_append_buf() returns jv_invalid_with_msg("String too long"), the raw-file loop does not stop.

If the file contains at least one more byte, the next loop iteration appends a new chunk to an object that is already invalid. With assertions enabled this aborts in jvp_string_ptr().

With assertions disabled, the invalid object is interpreted as a string object and ASan reports heap-buffer-overflow. This vulnerability is fixed in 1.8.2.

This vulnerability allows an attacker to trigger a heap out-of-bounds write by providing a specially crafted, oversized file to the `jq --rawfile` option. This can lead to a denial of service (DoS), making the affected system or application unavailable, and may also impact data integrity.

Exploitation requires user interaction, as a user must process the malicious file. Exploitation requires a local user to explicitly process an attacker-controlled file.

Red Hat severity: Moderate — CVSS 6.6 (CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:H). Weakness: CWE-787.