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Fencer Intel
low 2.4

CVE-2026-18503 json

Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()

published 2mo ago modified 17d ago also BIT-libpython-2026-18503 , BIT-python-2026-18503 , BIT-python-min-2026-18503 , EUVD-2026-55630

cvss
2.4
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits
0
none known

Summary

Attacker-controlled CSV samples can trigger super-linear regular-expression work during dialect sniffing and consume significant CPU when applications pass unbounded input to csv.Sniffer.sniff().

Patch / fix

  • bitnami libpython 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7
  • bitnami python 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7
  • bitnami python-min 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7
  • Python Software Foundation CPython 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7, 3.15.0rc1, 3.16.0
  • pypy3 Debian 14 8.0.1+dfsg-1
  • python3.11 Debian 12 3.11.2-6+deb12u9
  • python3.14 Debian 14 3.14.7-1
  • python3.15 Debian 14 3.15.0~rc1-1

debian advisories DEBIAN-CVE-2026-18503

  • python3.12 hummingbird 1 3.12.14-1.hum1
  • python3.12-idle hummingbird 1 3.12.14-1.hum1
  • python3.12-libs hummingbird 1 3.12.14-1.hum1
  • python3.12-test hummingbird 1 3.12.14-1.hum1
  • python3.12-tkinter hummingbird 1 3.12.14-1.hum1
  • python3.11 hummingbird 1 3.11.16-1.hum1
  • python3.11-idle hummingbird 1 3.11.16-1.hum1
  • python3.11-libs hummingbird 1 3.11.16-1.hum1

red hat advisories RHSA-2026:58420RHSA-2026:57660RHSA-2026:57010RHSA-2026:54554RHSA-2026:54534

  • python3 SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 3.6.15-150300.10.129.1
  • python3-core SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +12 more 3.6.15-150300.10.129.1
  • python SLE Module for Package Hub 15 SP7 2.7.18-150000.133.1
  • python-base SLE Module for Package Hub 15 SP7 2.7.18-150000.133.1
  • python313 SLE Module for Python 3 15 SP7 3.13.15-150700.4.56.1
  • python313-core SLE Module for Python 3 15 SP7 3.13.15-150700.4.56.1
  • python3 SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 3.4.10-25.199.1
  • python3-base SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 3.4.10-25.199.1

suse advisories SUSE-SU-2026:4754-1SUSE-SU-2026:4744-1SUSE-SU-2026:4743-1SUSE-SU-2026:4633-1SUSE-SU-2026:4411-1SUSE-SU-2026:4401-1

  • python313 openSUSE Tumbleweed 3.13.15-1.1
  • python315 openSUSE Tumbleweed 3.15.0~rc2-1.1

opensuse advisories openSUSE-SU-2026:11817-1openSUSE-SU-2026:11748-1

  • python3 Azure Linux 3.0 3.12.14-1

azure linux advisories AZL-95619

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Is CVE-2026-18503 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2026-18503 updated cvss 2.8

python: Python: Denial of Service via super-linear regular expression work in csv.Sniffer.sniff()

  • Red Hat Exploit Intelligence exploit-intelligence-tech-preview/vulnerability-analysis-rhel9 Red Hat Enterprise Linux 6 python, tkinter, python-libs, python-test, python-tools Red Hat Enterprise Linux 7 python, tkinter, python-libs, python-test, python-tools Red Hat Enterprise Linux 8 scipy, python3, python36, python3.12, python-nose, python-wheel, +31 more Red Hat Enterprise Linux 9 python3, python3.9, python3-idle, python3-libs, python3-test, python3-tkinter, +1 more Red Hat Enterprise Linux 10 python3.12
    +6 more products
    Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9 Red Hat Enterprise Linux command line assistant rhel-cla/rhel-knowledge-bridge-rhel10 Red Hat OpenShift AI (RHOAI) rhoai/odh-workbench-codeserver-datascience-cpu-py312-rhel9 Red Hat OpenShift Dev Spaces devspaces/code-rhel9 Red Hat OpenShift Virtualization 4 container-native-virtualization/ocp-virt-validation-checkup-rhel9 Red Hat Self-service automation portal 2 ansible-automation-platform/bootc-automation-portal-rhel9
    affected: workaround, no fix available “Do not pass untrusted or unbounded CSV input to csv.Sniffer.sniff(). If dialect detection is needed, limit the size of the sample passed to sniff() or use a known dialect directly with csv.reader().”
  • Red Hat Hardened Images python3 3.14.7-1.hum1, python3.14 3.14.7-1.hum1, python3.10 3.10.21-1.hum1, python3.11 3.11.16-1.hum1, python3.12 3.12.14-1.hum1, python3.13 3.13.15-1.hum1, +27 more
    fixed: vendor fix “Do not pass untrusted or unbounded CSV input to csv.Sniffer.sniff(). If dialect detection is needed, limit the size of the sample passed to sniff() or use a known dialect directly with csv.reader().” RHSA-2026:54534

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
none
Automatable
no
Technical impact
partial
Assessed
2mo ago

Exploit prediction

0.12% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 2.4 CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
CNA 4.0 2.4 CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:L/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 packages

ecosystem package affected fixed in
bitnami libpython
<3.10.21
>=3.11.0, <3.11.16
>=3.12.0, <3.12.14
>=3.13.0, <3.13.15
>=3.14.0, <3.14.7
3.10.21
3.11.16
3.12.14
3.13.15
3.14.7
bitnami python
<3.10.21
>=3.11.0, <3.11.16
>=3.12.0, <3.12.14
>=3.13.0, <3.13.15
>=3.14.0, <3.14.7
3.10.21
3.11.16
3.12.14
3.13.15
3.14.7
bitnami python-min
<3.10.21
>=3.11.0, <3.11.16
>=3.12.0, <3.12.14
>=3.13.0, <3.13.15
>=3.14.0, <3.14.7
3.10.21
3.11.16
3.12.14
3.13.15
3.14.7

Affected products

  • Python Software Foundation CPython

Classification

Weakness

References

Sources

Fencer Intel 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.