CVE-2026-39979
MediumCVSS 6.5Exploitation Probability (EPSS)
Low risk43th percentile - higher than 43% of all known CVEs
Summary
In the libjq library (part of the jq tool), the jv_parse_sized() function has an out-of-bounds read vulnerability. When processing malformed JSON in a non-NUL-terminated buffer, the error formatting function uses %s which reads until a NUL terminator, ignoring the caller-supplied length.
Risk Assessment
An attacker can exploit this vulnerability to disclose memory contents or cause a process crash, posing a risk to system confidentiality and availability.
Recommendation
Immediately update libjq to a version containing commit 2f09060afab23fe9390cce7cb860b10416e1bf5f or later. If an update is not possible, restrict access to jv_parse_sized() for untrusted input.
Other vulnerabilities in jq
See all- CVE-2016-4074High
The jv_dump_term function in jq 1.5 allows remote attackers to cause a denial of service via a crafted JSON file, leading to stack consumption and application crash. This issue has been fixed in jq 1.6_rc1-r0.
- CVE-2024-53427Medium
The decNumberCopy function in decNumber.c in jq through 1.7.1 does not properly consider that NaN is interpreted as numeric, which has a resultant stack-based buffer overflow and out-of-bounds write. This can be demonstrated by using --slurp with subtraction, such as a filter of .-. when the input has a certain form.
- CVE-2015-8863Critical
Off-by-one error in the tokenadd function in jv_parse.c in jq allows remote attackers to cause a denial of service (crash) via a long JSON-encoded number, which triggers a heap-based buffer overflow.
- CVE-2026-40164High
Before commit 0c7d133c3c7e37c00b6d46b658a02244fdd3c784, jq used MurmurHash3 with a hardcoded, publicly visible seed (0x432A9843) for all JSON object hash table operations, allowing an attacker to precompute key collisions offline. A crafted JSON object (~100 KB) with all keys hashing to the same bucket degrades lookups from O(1) to O(n), causing CPU exhaustion.
- CVE-2026-39956Medium
jq is a command-line JSON processor. Prior to version 1.8.2, the _strindices builtin in jq's src/builtin.c passes its arguments directly to jv_string_indexes() without verifying they are strings, and jv_string_indexes() in src/jv.c relies solely on assert() checks that are stripped in release builds compiled with -DNDEBUG. This allows an attacker to crash jq trivially with input like _strindices(0), and by crafting a numeric value whose IEEE-754 bit pattern maps to a chosen pointer, achieve a controlled pointer dereference and limited memory read/probe primitive.
Original NVD description (English source)
jq is a command-line JSON processor. In commits before 2f09060afab23fe9390cce7cb860b10416e1bf5f, the jv_parse_sized() API in libjq accepts a counted buffer with an explicit length parameter, but its error-handling path formats the input buffer using %s in jv_string_fmt(), which reads until a NUL terminator is found rather than respecting the caller-supplied length. This means that when malformed JSON is passed in a non-NUL-terminated buffer, the error construction logic performs an out-of-bounds read past the end of the buffer. The vulnerability is reachable by any libjq consumer calling jv_parse_sized() with untrusted input, and depending on memory layout, can result in memory disclosure or process termination. The issue has been patched in commit 2f09060afab23fe9390cce7cb860b10416e1bf5f.