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CVE-2026-118694

python-markdown2 through 2.5.5 Denial of Service via Unclosed Inline Link Destinations

8.7 HighFix available

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.45%Unchanged since Oct 29, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.7

python-markdown2 through 2.5.5 Denial of Service via Unclosed Inline Link Destinations

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Record
CVE-2026-118694
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-407
Updated
2026-11-02
EUVDEUVD-2026-112495 8.7

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Record
EUVD-2026-112495
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-rgrp-3mvm-5g9j 8.7

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote...

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Record
GHSA-rgrp-3mvm-5g9j
CVSS 4.0
8.7 HighCVSS: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
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-407
Updated
2026-11-02
NVD 8.7

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Record
CVE-2026-118694
CVSS 4.0
8.7 HighCVSS: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
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-407
Updated
2026-11-02
OSV 8.7

python-markdown2 through 2.5.5 Denial of Service via Unclosed Inline Link Destinations

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Record
CVE-2026-118694
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-407
Updated
2026-11-05
OSVDEBIAN-CVE-2026-118694 8.7

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Record
DEBIAN-CVE-2026-118694
CVSS 4.0
8.7 HighCVSS: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
Updated
2026-11-02
OSVUBUNTU-CVE-2026-118694 8.7

python-markdown2 through 2.5.5 contains a denial of service vulnerability that allows remote users to exhaust CPU by submitting Markdown with unclosed inline link destinations. Attackers can submit repeated '[a](' or '![a](' sequences, causing _find_balanced to rescan the remaining document for each link and consume quadratic CPU time.

Record
UBUNTU-CVE-2026-118694
CVSS 4.0
8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-05
OSVopenSUSE-SU-2026:12422-1 No score

python313-markdown2-2.5.5-3.1 on GA media

These are all security issues fixed in the python313-markdown2-2.5.5-3.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:12422-1
Updated
2026-11-05

Affected products

Affected packages

Affected packages
PackageAffectedFixed
python-markdown2
Debian:12
 All versions, plus listed versions
2.4.1-12.4.11-12.5.3-1~exp12.5.4-12.5.4-22.5.4-32.5.4-4
 None known
python-markdown2
Debian:13
 All versions, plus listed versions
2.4.11-12.5.3-1~exp12.5.4-12.5.4-22.5.4-32.5.4-4
 None known
python-markdown2
Debian:14
 All versions, plus listed versions
2.4.11-12.5.3-1~exp12.5.4-12.5.4-22.5.4-32.5.4-4
 None known
python-markdown2
Ubuntu:20.04:LTS
 All versions, plus listed versions
2.3.7-2
 None known
python-markdown2
Ubuntu:22.04:LTS
 All versions, plus listed versions
2.3.10-1.12.4.1-1
 None known
python-markdown2
Ubuntu:24.04:LTS
 All versions, plus listed versions
2.4.1-12.4.11-1
 None known
python-markdown2
Ubuntu:26.10
 All versions, plus listed versions
2.5.4-3
 None known
python-markdown2
Ubuntu:26.04:LTS
 All versions, plus listed versions
2.4.11-12.5.4-22.5.4-3
 None known
python-markdown2
openSUSE:Tumbleweed
 before 2.5.5-3.1
2.5.5-3.1

History

History
RecordedChangedSources
affected, aliases, facts, referencesOSV
factsOSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-118694 is a high vulnerability (CVSS 8.7) in Python-markdown2, published October 28, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.45%, the 39th percentile. Fixed in python-markdown2 2.5.5-3.1.

References

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