CVE-2021-3517
No exploitation reported by the sources we read.
- Published2021-05-19
- WeaknessCWE-125 · CWE-787
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
There is a flaw in the xml entity encoding functionality of libxml2 in versions before 2.9.11. An attacker who is able to supply a crafted file to be processed by an application linked with the affected functionality of libxml2 could trigger an out-of-bounds read. The most likely impact of this flaw is to application availability, with some potential impact to confidentiality and integrity if an attacker is able to use memory information to further exploit the application.
Timeline
dates in UTC- 2021-05-1914:15CVE publishedNVD
- 2026-10-2319:23EPSS crossed 10 %FIRST EPSS
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-3517?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-3517?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 33.x | = 33 | no fix published | NVD |
| 34.x | = 34 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 13.4 | = 13.4.0.0 | no fix published | NVD |
| 13.5 | = 13.5.0.0 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 13.4 | = 13.4.1.0 | no fix published | NVD |
| 13.5 | = 13.5.1.0 | no fix published | NVD |
26 more products in the sources.
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Distribution builds and vendor advisories
Packages from OSV.dev and products from the vendors' CSAF advisories.
version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.
Packages
- libxml2-develAlmaLinux:8all versions · fixed in 2.9.7-9.el8_4.2
Fix
Advisories and patches
- bugzilla.redhat.comPatch
- www.oracle.comPatch
- www.oracle.comPatch
- www.oracle.comPatch
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- CISA-ADPSSVC decisionnone2025-12-02
- OpenCVESSVC decisionnone—
- CISA-ADPCVSS 3.18.62025-12-02
- NVDCVSS 3.18.6read 2026-10-23
- NVDCVSS 2.07.5read 2026-10-23
- CISA-ADPweakness (CWE)CWE-1252025-12-02
- CNAweakness (CWE)CWE-787read 2026-10-23
- NVDweakness (CWE)CWE-787read 2026-10-23
- FIRST EPSSEPSS score17.0 %read 2026-10-23
- OSVaffected packages—
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
- Published
- 2021-05-19
- Last Modified
- 2026-10-14
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-3517?
Is CVE-2021-3517 actively exploited?
What is the CVSS score for CVE-2021-3517?
Running libxml2-devel? Hear about its next vulnerability
Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.