CVE-2026-54896

Description

### Summary `Oj.dump` in object mode is vulnerable to a heap buffer overflow when serializing Exception objects with a large `:indent` value. The serializer allocates a buffer sized for the object's attributes but does not account for the indent bytes added on each write. With `indent: 5000`, the accumulation of 5,000-byte indent strings overflows the 13,150-byte heap allocation, corrupting adjacent heap memory. ### Version - **Software**: oj gem - **Affected**: all versions with `ext/oj/dump.h` - **Latest tested**: 3.17.1 (confirmed present) ### Details `ext/oj/dump.h`, line 75–77: ```c static void fill_indent(Out out, int depth) { if (0 < out->opts->indent) { memset(out->buf + out->cur, ' ', (size_t)(out->opts->indent * depth)); ``` When dumping an Exception object in `:object` mode, `dump_obj_attrs` calls `fill_indent` repeatedly for each attribute. The buffer is pre-allocated based on the serialized content but not the indentation overhead. With `indent: 5000` the indent block for a nested object exceeds the remaining buffer space, producing a heap-buffer-overflow of size 5,000 at the end of the allocated region. ASAN report: ``` ==101656==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x527000022c5e WRITE of size 5000 at 0x527000022c5e thread T0 #0 memset #1 fill_indent /ext/oj/dump.h:77 #2 dump_obj_attrs /ext/oj/dump_object.c:552 #3 dump_obj /ext/oj/dump_object.c:80 #4 oj_dump_obj_val /ext/oj/dump_object.c:708 #5 oj_dump_obj_to_json_using_params /ext/oj/dump.c:817 #6 dump_body /ext/oj/oj.c:1429 #7 dump /ext/oj/oj.c:1480 0x527000022c5e is located 0 bytes after 13150-byte region [0x52700001f900, 0x527000022c5e) ``` ### Reproduce ```ruby require "oj" obj = Oj.load('{"^o":"RuntimeError"}', mode: :object) Oj.dump(obj, mode: :object, indent: 5000) ``` ### Workarounds This is at the discretion of the developer and not a public facing option so the workaround is the develop should not use extreme indents and should not offer the option for users to dump Ruby data with unlimited indentation size.

How to fix CVE-2026-54896

To remediate CVE-2026-54896, upgrade the affected package to a fixed version below.

• —upgrade to 3.17.3 or later

Is CVE-2026-54896 being exploited?

No exploitation signal available. Neither CISA KEV nor a current EPSS score has been published for CVE-2026-54896.