Medium [CVE-2026-54902] Use-After-Free in Oj::Parser SAJ Long Key Callback
This medium-severity Red Hat Linux advisory covers CVE-2026-54902.
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Summary
Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. Prior to version 3.17.2, is vulnerable to Use-After-Free when in SAJ mode.
The Oj::Parser does not protect cached object keys (≥ 35 bytes) from garbage collection, and a Ruby callback that triggers GC inside hash_end can cause the key string to be reclaimed while the C parser still holds a pointer to it.
The subsequent access to the freed string VALUE results in a segfault, confirmed by an RIP pointing to address 0x4242 (a canary-style pattern suggesting control over the freed memory's content). This issue has been fixed in version 3.17.2.
Red Hat's only product shipping the Oj Ruby gem (Compliance Backend) already includes version 3.17.3, which contains the fix for this vulnerability. No Red Hat products are affected.
Red Hat severity: Moderate.
- < 3.17.2
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
Mitigation
Upgrade to a fixed release: 3.17.2. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
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