CVE intelligence and bounded remediation
CVE-2020-24240 — GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when a '\0' byte is encountered
GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when a '\0' byte is encountered. NOTE: there is a risk only if Bison is used with untrusted input, and the observed bug happens to cause unsafe behavior with a specific compiler/architecture. The bug report was intended to show that a crash may occur in Bison itself, not that a crash may occur in code that is generated by Bison.
- Severity
- High
- CVSS
- 7.1 (2.0)
- Published
- 2020-08-25
- CISA KEV
- Not currently listed
- Ecosystem
- software/application
- Weaknesses
- CWE-416
Affected products
- gnu / bison / 3.7
Matched remediation archetype
Use-after-free, double free, and expired resource use
This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.
Check exposure
- Trace ownership, references, callbacks, asynchronous tasks, and teardown paths around the affected object or resource.
- Identify reachable inputs and timing or state transitions that can release the object while references remain.
- Confirm affected builds, allocators, feature flags, architectures, and process privileges.
Remediate safely
- Apply the maintained ownership or lifetime fix and rebuild all artifacts containing the affected native code.
- Use explicit ownership, safe reference management, cancellation and join semantics, and idempotent teardown.
- Add deterministic lifetime tests plus isolated sanitizer and concurrency coverage for shutdown and error paths.
Authoritative sources
Complete CVE record and remediation plan
The detailed catalog view below loads this exact record, its source evidence, and the full seven-phase agentic change plan.