Buffer overflow in Xmlsoft Libxml2
CVE-2026-11979
libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --shell mode. The usershell() function processes user input using fixed-size stack buffers without proper bounds checking. By supplying an overly long input line, an attacker can overflow internal buffers (command, arg, and argv) during input parsing. This results in memory corruption within the stack frame. Successful exploitation may cause a crash or potentially allow arbitrary code execution in the context of the xmlcatalog process. This issue has been fixed in the commit c2e233fc. NOTE: The maintainers of this project did not agree that this issue is a vulnerability and considered it a bug.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.001 (3.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 3rd percentile — 3.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.001 · newest: 0.001 · change: 0.000
Affected products
- Xmlsoft Libxml2 — versions 0
Weakness classification (CWE)
References
- cert.pl/en/posts/2026/06/CVE-2026-11979 (Third Party Advisory, third-party-advisory)
- gitlab.gnome.org/GNOME/libxml2/-/commit/c2e233fc1b341685fc99621b2768b503f777a72e (Patch, patch)
Frequently asked questions
- What is CVE-2026-11979?
- CVE-2026-11979 is a high-severity vulnerability in Xmlsoft Libxml2, classified under Stack-based Buffer Overflow. CVSS score: 7.8/10. Published 2026-06-29.
- How severe is CVE-2026-11979?
- High severity. CVSS v3 base score is 7.8 out of 10.