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CVE-2018-11503: The isfootnote function in markdown.c in libmarkdown.a in DISCOUNT 2.2.3a allows remote attackers to cause...

The isfootnote function in markdown.c in libmarkdown.a in DISCOUNT 2.2.3a allows remote attackers to cause a denial of service (heap-based buffer over-read) via a crafted file, as demonstrated by mkd2html.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2018-11503 is a denial-of-service flaw in Discount 2.2.3a, a Markdown processing library/tool. A crafted Markdown file can trigger a heap-based buffer over-read in footnote parsing, potentially crashing processing. Business impact is mainly availability for services that parse untrusted Markdown.

Executive priority

Treat this as a targeted availability risk, not an emergency without exposed Markdown parsing. Prioritize patching internet-facing or customer-content workflows first, then internal content pipelines using Discount.

Technical view

The issue is in the isfootnote function in markdown.c within libmarkdown.a in DISCOUNT 2.2.3a. The CVE describes a heap-based buffer over-read reachable through a crafted file, demonstrated with mkd2html. Public source data does not provide CVSS, CWE, exact fixed upstream version, or confirmed exploitation.

Likely exposure

Exposure is most likely where Discount/libmarkdown or mkd2html processes Markdown supplied by users, customers, uploads, tickets, comments, or automated content pipelines. Systems only processing trusted local Markdown have lower practical exposure.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation evidence. The described attacker outcome is denial of service through malformed input, not code execution. Remote impact depends on whether an internet-facing service feeds untrusted Markdown into affected Discount code.

Researcher notes

Evidence is limited to the CVE description, GitHub issue reference, and Debian advisories. Affected metadata in the bundle is incomplete, and no CVSS or CWE is provided. Do not infer broader products beyond Discount/libmarkdown/mkd2html.

Mitigation direction

  • Update Discount or Debian discount packages using vendor security advisories.
  • Check upstream Discount guidance for the fixed release or maintained branch.
  • Avoid processing untrusted Markdown with Discount 2.2.3a until patched.
  • Run Markdown conversion in isolated workers with resource and restart controls.
  • Restrict upload or content paths that feed Discount where feasible.

Validation and detection

  • Inventory systems for Discount, libmarkdown, and mkd2html usage.
  • Identify workflows that parse user-controlled Markdown files or text.
  • Compare installed package versions against Debian or upstream security guidance.
  • Confirm patched packages are deployed on all Markdown-processing hosts.
  • Review monitoring for repeated Markdown conversion crashes or worker restarts.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.