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Fencer Vulns
high 7.5

CVE-2026-115506 json

libexpat through 2.9.0 Denial of Service via Billion Laughs Detection Delay

published 2026-10-22 17 d ago modified 2026-11-02 6 d ago also EUVD-2026-108338

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 39%
public exploits
0
none known

Summary

libexpat through 2.9.0 contains a denial of service vulnerability because billion laughs protection in accountingDiffTolerated() in xmlparse.c detects entity amplification too late. Attackers can supply a moderately sized XML document with a large DTD and nested entity expansions to consume tens of seconds of CPU per parse.

Patch / fix

  • expat Debian 14 2.10.0-1

debian advisories DEBIAN-CVE-2026-115506

  • expat openSUSE Tumbleweed 2.10.0-1.1

opensuse advisories openSUSE-SU-2026:12396-1

  • expat Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 2.10.0-r0

alpine advisories ALPINE-CVE-2026-115506

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-115506 updated cvss 7.5

expat: expat: Denial of Service via delayed entity amplification detection

  • Red Hat Enterprise Linux 7 firefox, firefox 140.17.0-1.el10_2 Red Hat Enterprise Linux 8 expat, firefox, mingw-expat, thunderbird, mingw32-expat, mingw64-expat, +3 more Red Hat Enterprise Linux 9 expat, firefox, firefox-x11, thunderbird, expat 2.7.3-1.el10_2.5, firefox 140.17.0-1.el10_2, +1 more Red Hat Enterprise Linux 10 expat 2.7.3-1.el10_2.5, firefox 140.17.0-1.el10_2, thunderbird 140.17.0-1.el10_2 Red Hat Hardened Images expat 2.7.3-1.el10_2.5
    affected: workaround, no fix available
  • Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    affected: workaround, no fix available, no fix planned “Will not fix”
  • Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 6 expat, compat-expat1, expat 2.7.3-1.el10_2.5 Red Hat Enterprise Linux 7 expat, expat 2.7.3-1.el10_2.5 Red Hat Enterprise Linux 8 xmlrpc-c, xmlrpc-c-c++, xmlrpc-c-client, xmlrpc-c-client++
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
16 d ago

Exploit prediction

0.45% chance of exploitation in the next 30 days, higher than 39% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/hannob/lololol referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • libexpat libexpat

Classification

Weakness
  • CWE-776 Improper Restriction of Recursive Entity References in DTDs

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.