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CVE-2026-59922VulnerabilityPublished

Mistune: Prior to 3.3.0, a run of closed tilde, equals-sign, or caret marker pairs around a character causes quadratic

Affects mistuneSource GCVE Database

0
Authoritative record:CVE-2026-59922· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in 1.4.0_6 : patch mistune soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.4.0_6, 5.1.2_4
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 8 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade adr-viewer to 1.4.0_6; recon-ng to 5.1.2_4.

Affected software

ProductAffectedFixed in
Ubuntu 16.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=xenialOther threatsAffected
  • =0.6-2
  • =0.7.1-1
Fixed in–
Ubuntu 18.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=bionicOther threatsAffected
  • 0.7.4-1 – 0.8.3-2
4 affected builds
Fixed in–
Ubuntu 20.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=focalOther threatsAffected
  • =0.8.4-1
  • =0.8.4-2
Fixed in–
Ubuntu 22.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=jammyOther threatsAffected
  • =0.8.4-4
  • =0.8.4-5
  • =2.0.0-1+really0.8.4-1
Fixed in–
Ubuntu 24.04 LTSmistunepkg:deb/ubuntu/mistune?arch=source&distro=nobleOther threatsAffected
  • =2.0.4-2
  • =3.0.2-1
Fixed in–
Ubuntu 25.10mistunepkg:deb/ubuntu/mistune?arch=source&distro=questingOther threatsAffected
  • =3.0.2-2
  • =3.1.3-1
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available in Mistune versions 1.4.0_6 and 5.1.2_4 that resolves the quadratic-time parsing inefficiency. Users should upgrade to these or later versions to mitigate the vulnerability.

Description

Mistune versions prior to 1.4.0_6 and 5.1.2_4 contain a denial of service vulnerability due to quadratic-time parsing when processing long sequences of repeated markdown markers. This leads to excessive CPU usage when rendering crafted inputs. A patch is available to fix this issue.

References

Community reviews

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