Security readout for executives and security teams
Plain-English summary
GNU Bison before 3.7.1 could crash or behave unsafely when processing input containing a null byte. This matters mainly where Bison itself processes untrusted files, such as automated build or analysis services. The CVE notes this is not evidence that Bison-generated code is affected.
Executive priority
Treat as low priority unless your organization runs Bison as a service or in automated pipelines handling untrusted source packages. For normal software consumption, the cited evidence points to limited operational exposure.
Technical view
The issue is a use-after-free in _obstack_free in lib/obstack.c, reached from gram_lex when a '\0' byte is encountered. The CVE notes unsafe behavior was observed only with a specific compiler and architecture, and frames the demonstrated impact as a crash in Bison itself.
Likely exposure
Exposure is most likely in developer workstations, package builders, CI systems, or web services that run GNU Bison before 3.7.1 on untrusted input. Systems only running parsers generated by Bison are not identified as affected by the cited CVE text.
Exploitation context
No active exploitation is cited, and this CVE is not listed as KEV in the supplied bundle. Practical risk depends on whether attackers can supply files to Bison. The public description emphasizes a Bison process crash scenario, not compromise of generated parser code.
Researcher notes
Key uncertainty remains exploitability beyond crash behavior. The CVE specifically narrows risk to untrusted Bison input and compiler/architecture-dependent unsafe behavior. Focus validation on build pipeline exposure and exact Bison versions rather than downstream generated code.
Mitigation direction
- Upgrade GNU Bison to 3.7.1 or later where feasible.
- Do not run vulnerable Bison versions on untrusted grammar input.
- Restrict CI or build services that accept external source packages.
- Check GNU Bison release notes or vendor packages for backported fixes.
Validation and detection
- Inventory hosts, containers, and CI images for GNU Bison versions before 3.7.1.
- Identify workflows where Bison processes externally supplied files.
- Confirm package manager advisories or changelogs show the relevant fix.
- Verify generated parser consumers are not misclassified as directly affected.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2020-24240 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/akimd/bison/commit/be95a4fe2951374676efc9454ffee8638faaf68dCVE reference · x_refsource_MISC
- https://lists.gnu.org/r/bug-bison/2020-07/msg00051.htmlCVE reference · x_refsource_MISC
- https://github.com/akimd/bison/compare/v3.7...v3.7.1CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.