CVE-2026-49839

Description

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.

CVSS v3.1 Score

7.1

HIGH

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

EPSS — Exploit Prediction

0.0017

Probability of exploitation

0.06%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-787 Out-of-bounds Write

Affected Products

Vendor	Product	Versions
jqlang	jq	< 1.8.2

References

Advisories & Patches

https://github.com/jqlang/jq/security/advisories/GHSA-cfh2-vwfq-qfmm https://github.com/jqlang/jq/security/advisories/GHSA-cfh2-vwfq-qfmm

Exploits

https://github.com/jqlang/jq/security/advisories/GHSA-cfh2-vwfq-qfmm https://github.com/jqlang/jq/security/advisories/GHSA-cfh2-vwfq-qfmm

Frequently Asked Questions

What is CVE-2026-49839? +

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. It has a CVSS v3.1 base score of 7.1 (HIGH).

How severe is CVE-2026-49839? +

CVE-2026-49839 has a CVSS v3.1 score of 7.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0017, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-49839? +

CVE-2026-49839 affects products from jqlang, specifically: jq. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-49839? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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