CVE-2018-25032 is a high-severity (CVSS 7.5) Out-of-bounds Write vulnerability in nokogiri. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for nokogiri — see the affected versions and patch details below.
Nokogiri affected by zlib's Out-of-bounds Write vulnerability
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2018-25032.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
nokogiriReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
zlib before 1.2.12 allows memory corruption when deflating (i.e., when compressing) if the input has many distant matches.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | nokogiri | all versions | 1.13.4bundle update nokogiri --conservative |
Affected Products
mac os xapplemacosapplezuluazuldebian linuxdebianfedorafedoraprojectgotoassistgotoResearch 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 nokogiri, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nokogiri to 1.13.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-25032 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.
This bug was introduced in zlib v1.2.2.2 through zlib v1.2.11, with the addition of the Z_FIXED option, which forces the use of fixed Huffman codes, rather than dynamic Huffman codes, allowing for a simpler decoder for special applications. This bug is difficult to trigger, as Z_FIXED is usually only used in special…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 6 Extended Lifecycle Support | zlib-0:1.2.3-31.el6_10 | RHSA-2022:2214 |
| Red Hat Enterprise Linux 7 | zlib-0:1.2.7-20.el7_9 | RHSA-2022:2213 |
| Red Hat Enterprise Linux 7.4 Advanced Update Support | zlib-0:1.2.7-17.el7_4.1 | RHSA-2023:0976 |
| Red Hat Enterprise Linux 7.6 Advanced Update Support | zlib-0:1.2.7-18.el7_6.1 | RHSA-2023:0975 |
| Red Hat Enterprise Linux 7.7 Advanced Update Support | zlib-0:1.2.7-18.el7_7.1 | RHSA-2023:0943 |
| Red Hat Enterprise Linux 8 | mingw-zlib-0:1.2.8-10.el8 | RHSA-2022:7813 |
| Red Hat Enterprise Linux 8 | zlib-0:1.2.11-18.el8_5 | RHSA-2022:1642 |
| Red Hat Enterprise Linux 8 | rsync-0:3.1.3-14.el8_6.2 | RHSA-2022:2201 |
Frequently Asked Questions
Is CVE-2018-25032 in your dependencies?
Find it across RubyGems, including transitive dependencies.