CVE-2021-47996

HIGH
Published Aug 25, 2026 Modified Aug 28, 2026 CWE-119

Description

Nokogiri before 1.11.4 (CRuby implementation only, when the packaged/vendored libxml2 is used) bundles libxml2 2.9.10, which is affected by multiple vulnerabilities addressed in libxml2 2.9.12, including a memory leak in xmlSchemaValidateStream (CVE-2019-20388), a global buffer over-read in xmlEncodeEntitiesInternal (CVE-2020-24977), a heap-based buffer overflow (CVE-2021-3517), and an out-of-bounds read (CVE-2021-3518). Processing crafted XML documents may lead to denial of service, information disclosure, or memory corruption.

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CVSS v3.1 Score

7.5
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0052
Probability of exploitation
0.42%
Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-119 Buffer Overflow

References

Other References

https://github.com/GNOME/libxml2/commit/0e1a49c8907645d2e155f0d89d4d9895ac5112b5 https://github.com/GNOME/libxml2/commit/1098c30a040e72a4654968547f415be4e4c40fe7 https://github.com/GNOME/libxml2/commit/1358d157d0bd83be1dfe356a69213df9fac0b539 https://github.com/GNOME/libxml2/commit/50f06b3efb638efb0abd95dc62dca05ae67882c2 https://github.com/GNOME/libxml2/commit/7ffcd44d7e6c46704f8af0321d9314cd26e0e18a https://github.com/GNOME/libxml2/commit/8598060bacada41a0eb09d95c97744ff4e428f8e https://github.com/GNOME/libxml2/commit/babe75030c7f64a37826bb3342317134568bef61 https://github.com/GNOME/libxml2/commit/bf22713507fe1fc3a2c4b525cf0a88c2dc87a3a2 https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-7rrm-v45f-jp64 https://www.vulncheck.com/advisories/nokogiri-before-multiple-vulnerabilities-via-libxml2

Frequently Asked Questions

What is CVE-2021-47996? +
Nokogiri before 1.11.4 (CRuby implementation only, when the packaged/vendored libxml2 is used) bundles libxml2 2.9.10, which is affected by multiple vulnerabilities addressed in libxml2 2.9.12, including a memory leak in xmlSchemaValidateStream (CVE-2019-20388), a global buffer over-read in xmlEncodeEntitiesInternal (CVE-2020-24977), a heap-based buffer overflow (CVE-2021-3517), and an out-of-bounds read (CVE-2021-3518). Processing crafted XML documents may lead to denial of service, information disclosure, or memory corruption. It has a CVSS v3.1 base score of 7.5 (HIGH).
How severe is CVE-2021-47996? +
CVE-2021-47996 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0052, placing it in the 0th percentile for exploitation probability.
How do I check if I'm vulnerable to CVE-2021-47996? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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