CVE-2020-8244 is a medium-severity (CVSS 6.5) CWE-126 vulnerability in bl. 1 public exploit reference exists, so weaponization risk is real. A fix is available for bl — see the affected versions and patch details below.
Remote Memory Exposure in bl
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2020-8244 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
blnpmDescription
A buffer over-read vulnerability exists in bl <4.0.3, <3.0.1, <2.2.1, and <1.2.3 which could allow an attacker to supply user input (even typed) that if it ends up in consume() argument and can become negative, the BufferList state can be corrupted, tricking it into exposing uninitialized memory via regular .slice() calls.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | bl | all versions | 1.2.3npm install bl@1.2.3 |
| 📦npm | bl | ≥ 2.0.0&&< 2.2.1 | 2.2.1npm install bl@2.2.1 |
| 📦npm | bl | ≥ 3.0.0&&< 3.0.1 | 3.0.1npm install bl@3.0.1 |
| 📦npm | bl | ≥ 4.0.0&&< 4.0.3 | 4.0.3npm install bl@4.0.3 |
Affected Products
bufferlistbufferlist_projectdebian linuxdebianResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for bl, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update bl to 1.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-8244 is resolved across your whole dependency graph.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Frequently Asked Questions
Is CVE-2020-8244 in your dependencies?
Find it across npm, including transitive dependencies.